2a. susbsect. Cyclostigma (Griseb.) Müll. Arg.
2b. subsect. Sampatik G.L. Webster
2c. subsect. Palanostigma Mart. Ex Baill.

3. sect. Klotzschiphytum (Baill.) Baill.
4. sect. Eutropia (Klotzsch) Baill.
5. sect. Luntia (Raf.) G.L. Webster

5a. subsect. Cuneati G.L. Webster
5b. subsect. Matourenses G.L. Webster

6. sect Eluteria Griseb.
7. sect. Croton
8. sect. Ocalia (Klotzsch) Baill.
9. sect. Corylocroton G.L.Webster
10. sect. Anadenocroton G.L.Webster
11. sect. Tiglium (Klotzsch) Baill.
12. sect. Quadrilobus Müll. Arg.
13. sect. Cascarilla Griseb.
14. sect. Velamea Baill.
15. sect. Andrichnia Baill.
16. sect. Anisophyllum Baill.
17. sect. Furcaria Boivin ex Baill.
18. sect. Monguia Baill.
19. sect. Decapetalon Müll. Arg.
20. sect. Podostachys (Klotzsch) Baill.
21. sect. Octolobium Chodat & Hassl.
22. sect. Geiseleria (Klotzsch) Baill.
23. sect. Pilinophyton (Klotzsch) A. Gray
24. sect. Eremocarpus (Benth.) G.L.Webster
25. sect. Gynamblosis (Torr.) A. Gray
26. sect. Crotonopsis (Michx.) G.L.Webster
27. sect. Argyrocroton (Müll. Arg.)G.L.Webster
28. sect. Lamprocroton (Müll. Arg.) Pax
29. sect. Julocroton (Mart.) G.L.Webster
30. sect. Adenophyllum Griseb.
31. sect. Barhamia (Klotzsch) Baill.
32. sect. Decalobium Müll. Arg.
33. sect. Micranthis Baill.
34. sect. Medea (Klotzsch)Baill.
35. sect. Lasiogyne (Klotzsch) Baill.
36. sect. Argyroglossum Baill.
37. sect. Astraeopsis Baill.
38. sect. Codonocalyx Klotzsch ex Baill.
39. sect. Astraea (Klotzsch) Baill.
40. sect. Drepadenium (Raf.) Müll. Arg.


Croton L., Sp. Pl.: 1004. 1753 º Oxydectes Kuntze, Revis. Gen. Pl.: 609. 1891 (nom. superf.). -LT. (Webster, 1967): C. aromaticus L. (supersedes the earlier designation, accepted by Farr & al., 1979, of C. tiglium L. by Small (1913).

1. Croton sect. Cleodora (Klotzsch) Baill., Etude Euphorb.: 369. 1858

Monoecious trees or shrubs; indumentum appressed-stellate; leaves alternate, pinnately or palmately veined, glandular at base; inflorescences terminal lower cymules bisexual or sometimes unisexual; petals present in staminate, reduce or absent in pistillate flowers; sepals of staminate flowers imbricate; stamens 15-20; pistillate flowers distinctly pedicellate, sepals 5, basally connate and/or distinctly imbricate, entire; styles multifid.
This neotropical section of about 10 species (or less) has a curious disjunct distribution in Costa Rica, Amazonia, and eastern Brazil.

Representative species:

2. Croton sect. Cyclostigma Griseb., Fl. Brit. W. I.: 42. 1859.

Monoecious trees or shrubs; indumentum stellate; stems often exuding reddish sap; leaves alternate, mostly palmately veined or lobed, biglandular at base; inflorescences terminal, basal cymules bisexual; petals present in staminate flowers, usually reduced in pistillate flowers; stamens 11-100 or more; pistillate flowers distinctly pedicellate, sepals entire, eglandular, valvate or reduplicate-valvate; styles bifid to multifid.

As delimited here, sect. Cyclostigma includes 40-50 mainly neotropical species. The section is quite diverse, and tentatively may be divided into 3 subsections:

2a. Croton subsect. Cyclostigma (Griseb.) Müll. Arg. in Linnaea 34: 81. 1865.

Leaves palmately or pinnately veined, subentire or denticulate, copiously stellate beneath; stamens 15-65; calyx of pistillate flower not reduplicate-valvate; styles bifid. Mainly New World. Some species included by Müller (1866) probably do not belong here, including e.g. Croton suberosus Kunth with eglandular leaves.

Representative species:

2b. Croton subsect. Sampatik G.L. Webster, subsect. nov.

Leaves pinnately veined, crenate, sparsely appressed-stallate; stamens 10-20; pistillate flowers long-pedicellate; sepals of pistillate flower not reduplicate-valvate; styles bifid.

This new subsection is proposed to accommodate some South American species that differ from most other species of Croton sect. Cyclostigma in their elongated, nearly glabrous leaves and long inflorescence with unusually long-pedicellate pistillate flowers. The habit is reminiscent of some species in C. sect. Tiglium.

Representative species:

2c. Croton subsect. Palanostigma Mart. ex Baill., Etude Euphorb.: 358. 1858.

Leaves mostly palmately veined and copiously stellate beneath; stamens 10-100+; pistillate flowers distinctly pedicellate, sepals ± reduplicate-valvate; styles multifid.

There are no typical species of Croton subsect. Palanostigma confined to North America, although species such as C. smithianus Croizat extend north to Costa Rica and Nicaragua. C. grewiifolius Müll. Arg., although technically fitting into this subsection because of the quadrifid styles, differs in its nearly pinnately veined leaves. C. goudotii Baill. is excepcional in having both bisexual cymules and well-developed pistillate petals, as well as in its striking geographical disjunction from its American relatives.

The only neotropical species of Croton known to be lianas, C. adscendens Secco & N. Rosa and C. pullei Lanj., are close relatives in the Amazon forest (Secco & Rosa 1992). They appear to belong to C. subsect. Palanostigma because of their reproductive characters, although they differ in the climbing habit and short-pedicellate flowers. Possibly further study will show that these climbing species should be referred to a separate subsection.

Representative species:

• South America: Croton abutiloides Kunth, C. benthamianus Müll. Arg., C. caldensis Müll. Arg., C. callicarpifolius Vahl, C. celtidifolius Baill., C. coriaceus Kunth, C. fastuosus Baill., C. killipianus Croizat, C. lagoensis Müll. Arg., C. medusae Müll. Arg., C. polycarpus Benth., C. pycnanthus Benth., C. quadrisetosus Lam., C. rimbachii Croizat, C. smithianus Croizat, C. sordidus Benth., C. speciosus Müll. Arg., C. warmingii Müll. Arg.
• Madagascar: C. goudotii Baill.

3. Croton sect. klotzschiphytum Baill., in Adansonia 1: 169. 1861.

Monoecious trees or shrubs; indumentum of leaves depressed-stellate; leaves alternate, palmately veined, glandular at base; inflorescences terminal, not bisexual below; petals present in staminate and pistillate flowers; stamens 20-60; pistillate flowers pedicellate, sepals entire, valvate; styles bifid to multifid.

This section inthe strict sense would include only Croton mauritianus Lam. and C. boutonianus Müll. Arg. of Mauritius and Reunion. Its status must be regarded as dubious, since it differs from C. sect. Andrichnia only in the alternate leaves and larger stamen number.

Species included:

4. Croton sect. Eutropia (Klotzsch) Baill., Etude Euphorb.: 357. 1858.

Monoecious trees or shrubs; indumentum lepidote or stellate-lepidote; leaves alternate or opposite, palmately or pinnately veined, biglandular at base; stipules entire; inflorescences terminal, with bisexual cymules at base, bracts persistent; petals present in staminate flowers, reduced in pistillate flowers; sepals of staminate flower imbricate; stamens 10-15; pistillate flowers subsessile, sepals entire, imbricate; styles bifid (style-branches at most emarginate).

As circumscribed here (as monotypic), Croton sect. Eutropia is much smaller than in the treatments of Müller (1873, as subsection) and Pax & Hoffmann (1931), who included all of the species with bisexual lower cymules in the inflorescences. Even C. ser. Eutropia of Müller (C. subsect. Eutropia of Pax) is more inclusive, with all of the lepidote species of C.sect. Eutropia. However, the type species of C. sect. Eutropia, C. polyandrus, from coastal Brazil, differs from all the associated species in its pistillate flowers with discrete, distinctly imbricate sepals. The species assigned to C. sect. Eutropia by Müller (1873) seem better placed in either C. sect. Cleodora or sect. Luntia. There are a number of paleotropical species, such as C. argyratus Blume, C. insularis Baill., and C. macrostachys Del., that share characters with C. sect. Eutropia; however, until further studies can be made, it would be premature to include any of them in this section.

The relationships of Croton sect. Eutropia may be closest with C. sect. Cleodora, in which the sepals of the pistillate flowers are also (usually) distinctly imbricate. At present, it appears reasonable to maintain C. sect. Eutropia as distinct because its type, C. polyandrus, differs from the species of C. sect. Cleodora in having dentate leaves, persistent bracts, chorisepalous calyces, and bifid styles.

5. Croton sect. Luntia (Raf.) G.L. Webster, stat. nov.

Monoecious trees or shrubs; indumentum lepidote; leaves alternate, pinnately veined, entire, biglandular at base, stipules entire, deciduous; inflorescences terminal, often clustered, unisexual or bisexual, the latter with or without bisexual cymules at base; stamens 10-15; pistillate flowers subsessile or pedicellate, sepals entire and eglandular, valvate (or somewhat reduplicate); styles multifid.

This well-characterized section appears to be entirely neotropical, although there are some African species (e.g. Croton mubango Müll. Arg.) that might prove to be related. Jablonski (1965) treated the South American taxa under an informal designation ("C. matourensis" group). Species of C. sect. Luntia are easily distinguished from C. sect. Eutropia by their entire leaves and valvate sepals. Species of C. sect. Argyrocroton that have bisexual cymules are distinguishable from C. sect. Luntia by their bifid styles.

The species of Croton sect. Luntia fall into two distinctive groups that merit recognition as subsections:

5a. Croton subsect. Cuneati G.L. Webster, subsect. nov.

Leaves scattered-lepidote beneath; inflorescences staminate or bisexual, the latter (at least in part) usually with bisexual cymules at base; pistillate flowers subsessile (pediceles in flower shorter than calyx); sepals more or less free; capsules oblong (1 cm high or more).

Croton subsect. Cuneati includes about 10 species mainly of South America. Most of these were reviewed by Jablonski (1965), who proposed a number of very similar species that need to be critically evaluated.

Representative species:

• West Indies: Croton poecilanthus Urb.
• Panama and Colombia: C. pachypodus G.L. Webster.
• Amazonia: C. cuneatus Klotzsch, C. tessmannii Mansf.
• Guayana Highlands: C. kaieteuri Jabl., C. monachinoensis Jabl., C. neblinae Jabl., C. subcoriaceus Jabl. From Jablonski's description, it seems doubtful that C. pakaraimae Jabl. belongs here because of the imbricate sepals in the pistillate flower.

5b. Croton subsect. Matourensis G.L. Webster, subsect. nov.

Leaves usually metallic-lepidote beneath; inflorescences staminate or bisexual, without bisexual cymules at base; pistillate flowers long-pedicellate, calyx ± gamophyllous; fruit oblate (less than 1 cm high).

This primarily South American subsection includes only 2 closely related species that were first clearly descriminated by Lanjouw (1931). None of the other species enumerated by Jablonski (1965) appear to be closely related; these are mostly referable to Croton subsect. Cuneati.

Representative species:

• Panama and South America: Croton lanjouwensis Jabl.
• Venezuela to Brazil: C. matourensis Aubl.

6. Croton sect. Eluteria Griseb., Fl. Brit. W. I.: 39. 1859.

Monoecious trees or shrubs; indumentum of foliage lepidote; leaves alternate, entire and unlobed, pinnately or palmately veined, without petiolar glands; stipules rudimentary or absent; inflorescences mostly axillary, without bisexual cymules; petals present in both staminate and pistillate flowers; stamens mostly 10-16; pistilate flowers pedicellate, sepals entire, valvate, eglandular; ovary with stellate or lepidote trichomes; styles multifid.

As defined here, Croton sect. Eluteria is an entirely American group of about a dozen species. Old World species that were included in the section by Müller (1866) and by Pax & Hoffmann (1931), which differ in having leaves with laminar glands, are referable to C. sect. Andrichnia, sect. Klotzschiphytum, and sect. Monguia.

Representative species:

7. Croton sect. Croton [C. sect. Eucroton Baill., Etude Euphorb.: 354. 1858, nom. inval.]

Monoecious trees or shrubs; indumentum of foliage stellate; leaves alternate, unlobed, ± palmately veined, glandular at base; stipules entire; inflorescences terminal, without bisexual cymules; petals absent in pistillate flowers; stamens 15-35; pistillate flowers pedicellate, sepals entire, eglandular, valvate; ovary with stellate trichomes; styles multifid.

As here interpreted, Croton sect. Croton includes about 10 Old World species of the Mascarene islands, tropical Asia, and northern Australia. A few American species such as C. astrogynus Baill. and C. billbergianus Müll. Arg. would be referable here on the basis of their characters but are probably not closely related.

Representative species:

8. Croton sect. Ocalia (Klotzsch) Baill., Etude Euphorb.: 366. 1858.

Monoecious or dioecious shrubs; indumentum stellate; leaves alternate (sometimes opposite), unlobed, pinnately or palmately veined ± coarsely serrate, glandular at base; stipules entire; inflorescences terminal, without bisexual cymules; petals absent in pistillate flowers; stamens 7-12(15); sepals of pistillate flower entire, eglandular, valvate; ovary with stellate trichomes; styles multifid.

This section includes about 10 species with a disjunct distribution between North America, the West Indies, and extra-Amazonian Brazil. Judging from the description (Leonard 1962), Croton laciniatistylus Leon., an African species from Katanga, may be related to the Brazilian species.

Representative species:

9. Croton sect. Corylocroton G.L. Webster, sect. nov.

Monoecious trees or shrubs; indumentum stellate-lepidote; leaves alternate, pinnately veined, coarsely dentate, glandular at base; stipules entire, reduced; inflorescences terminal, with or without bisexual cymules; petals reduced in pistillate flowers; stamens 10-18; pistillate flowers subsessile or pedicellate, sepals entire, not glandular, valvate; styles bifid.

This small American section has a basically Caribbean distribution.

Species included:

10. Croton sect. Anadenocroton G.L. Webster, sect. nov.

Monoecious or dioecious shrubs; indumentum stellate; leaves alternate, pinnately veined, entire, without basal glands; stipules entire; inflorescences unisexual or bisexual, without basal bisexual cymules; stamens 10-15; pistillate flowers sessile or pedicellate, sepals entire, eglandular, valvate; petals absent; styles multifid.

The species of this section in some respects resemble Croton sect. Velamea, but differ in their multifid styles. C. axillaris diverges from the other species in its dioecious, axillary inflorescence production, but is similar in other characters.

Species included:

11. Croton sect. Tiglium (Klotzsch) Baill., Etude Euphorb.: 361. 1858.

Monoecious or dioecious shrubs or trees; indumentum sparse, appressed-stellate; leaves alternate, pinnately or palmately veined, glandular at base; stipules entire; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-20; pistillate sepals distinctly pedicellate, entire, eglandular, valvate, sometimes accresscent; styles bifid.

This section, as here defined, includes about 20 species of America and the Old World. In the strict sense, as treated by Müller (1866), Tiglium is a group of species with triplinerved leaves and inflated capsules. If the species with strictly pinnate venation were separated, they would fall into Baillon's Croton sect. Gymnocroton; however, it seems preferable to adopt a broader definition to emphasize the overall similarities.

Representative species:

12. Croton sect. Quadrilobus Müll. Arg. in Linnaea 34: 78. 1865.

Monoecious shrubs; indumentum sparse, appressed-stellate; leaves alternate, pinnately veined, glandular at base; stipules rudimentary; inflorescences apparently terminal, without bisexual cymules; petals absent in pistillate flowers; staments c. 11; pistillate flowers short-pedicellate, sepals entire, eglandular, valvate; styles bifid.

This monotypic section of Brazil scarcely differs from sect. Tiglium except in the tetramerous perianth. The single species, Croton sapiifolius, is still imperfectly known; when better studied, the section can perhaps be amalgamated with sect. Tiglium.

13. Croton sect. Cascarilla Griseb., Fl. Brit. W. I.: 38. 1859.

Monoecious (or sometimes dioecious) shrubs or trees; indumentum stellate, often dense; leaves alternate, pinnately veined, glandular at base; stipules entire; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-30; pistillate flowers mostly sessile or subsessile, sepals entire, eglandular, valvate; styles bifid (sometimes emarginate or lobed at tip).

As presently defined, this is the largest section of Croton, with over 100 species. In terms of the diagnostic characters used here, C. sect. Cascarilla only differs from C. sect. Velamea in having paired glands at the leaf base. The boundary between the two sections may be an artificial one, and both sections are probably unnatural.

However, there is a striking diffirence in geographic distribution, since C. sect. Cascarilla is present in the Old World as well as the New World. In contrast to C. sect. Velamea, the species in C. sect. Cascarilla are concentrated in the West Indies and South America, and are somewhat less well represented in mainland North America.

There are problems with discriminating Croton sect. Cascarilla from other sections. C. xalapensis Kunth resemble species of C. sect. Cyclostigma in leaf shape and stamen number. A number of neotropical species, such as C. jutiapensis Croizat and C. repens Schltdl., resemble C. sect. Ocalia in leaf morphology but have bifid styles. The evident diversity among species of C. sect. Cascarilla suggests that subdivisions into subsections would be desirable, but that will require much more study.

Representative species:

14. Croton sect. Velamea Baill. in Adansonia 4: 316. 1864.

Monoecious or dioecious shrubs, subshrubs, or herbs; indumentum stellate, often dense and trichomes pedicellate; leaves alternate, pinnately veined, eglandular at base; stipules entire; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-20; pistillate flowers sessile or short-pedicellate, sepals entire, eglandular, valvate; styles bifid.

This section includes a considerable number of widespread neotropical species. It appears that Croton sect. Velamea, with over 50 American species, may be confined to the New World, although it cannot be exluded that some Old World species may prove to belong here. For example, C. rivularis E. Mey ex Müll. Arg., from South Africa, possibly may belong to C. sect. Velamea on the basis of diagnostic characters. The section as here defined may prove to be unnatural, but it seems premature to attempt to discriminate the different species complexes.

Representative species:

15. Croton sect. Andrichnia Baill., Etude Euphorb.: 362. 1858.

Monoecious trees or shrubs; indumentum appressed-stellate; leaves opposite or subopposite (at least above), pinnately veined, glandular at base but without laminar glands; inflorescences pseudo-terminal, not bisexual below; petals present in staminate, present or reduced in pistillate flowers; stamens 10-20; pistillate flowers pedicellate, sepals entire, valvate; styles bifid to multifid.

This Old World section remains ill-defined. The type species, Croton bracteatus Lam., is unusual in its accrescent bracts, but C. nudatus Baill., associated with it by Müller (1866), appears not to have such striking bracts. These two species have multifid styles, and it is not clear whether they belong in the same section with such species as C. mongue Baill., with much denser and looser stellate pubescence and bifid styles. The common Madagascar species C. cassinoides Lam., although having eglandular leaves, may belong in this section.

Representative species:

16. Croton sect. Anisophyllum Baill., in Adansonia 1: 154, 170. 1861.

Monoecious trees or shrubs; indumentum appressed-stellate, often dense and pale; leaves mostly opposite, subopposite, or subverticellate, pinnately veinde, usually glandular at base and often on lamina beneath; inflorescences pseudoterminal, not bisexual below; petals reduced in pistillate flowers; stamens 15-20; pistillate flowers pedicellate, sepals entire, valvate; styles multifid.

Croton sect. Anisophyllum includes about 10-15 species of Madagascar. The section as defined by Baillon included C. muricatus Vahl, but that species was referred to C. sect. Eluteria by Müller (1866). Leandri (1939) included most of the species in his "groupe Adenophorum", and also treated C. payerianus as a synonym of the species such as C. cascarilloides, that have pseudo-verticillate leaves, should be referred to this section.

Representative species:

17. Croton sect. Furcaria Boivin ex Baill., Etude Euphorb.: 356. 1858.

Monoecious shrubs; indumentum of foliage sparse, appressed-stellate; leaves opposite or verticillate (at least distally), glandular or eglandular at base; stipules entire or reduced; inflorescences pseudoterminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 6-12; pistillate flowers ± pedicellate, sepals entire, eglandular, valvate; styles bifid.

The type species of this section, Croton boivinianus, is aberrant in its nearly eglandular leaves and reduced stamen number. However, a number of other Old World species with appressed-stellate indumentum can tentatively be associated with it.

Representative species:

18. Croton sect. Monguia Baill., in Adansonia 1: 146. 1861.

Monoecious trees or shrubs; indumentum lepidote; leaves opposite or subopposite (at least in part), pinnately veined, glandular at base; inflorescences pseudoterminal, not bisexual below; petals equalling sepals or reduced to obsolete pistillate flowers; stamens 10-35; pistillate flowers pedicellate, sepals entire, valvate; styles multifid or greatly dilated.

In the circumscription or Baillon, Croton sect. Monguia included 2 species, the lectotype plus C. argyrodaphne Baill. However, Müller (1866) reported the pistillate petals of the latter species as reduced ("subulata, exigua") and Leandri (1939) described them as absent. It is clear that only C. chrysodaphne corresponds to the regarded the specimens of C. chrysodaphne as representing a possibly "abnormal" form of C. chrysodaphne. Judging from other instances reported in the literature, it seems likely that development of pistillate petals is variable within C. chrysodaphne.

As defined here, Croton sect. Monguia includes the Madagascar species with opposite, glandular, lepidote leaves and multifid styles. It is not clear whether there are any extra-Malagasian species, although C. cascarilloides Raeusch. of southeast Asia is suggestively similar.

Representative species:

19. Croton sect. Decapetalon Müll. Arg. in Linnaea 34: 78. 1865.

Monoecious shrubs; indumentum of foliage lepidote; leaves opposite or subopposite, entire, pinnately veined, eglandular at base; stipule entire or obsolete; inflorescences pseudoterminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-15; pistillate sepals equal, entire, valvate; styles bifid.

When it was first defined by Müller (1865), no species were enumerated in Croton sect. Decapetalon, but in Candolle's Prodromus (Müller, 1866) he listed two: C. squamigerus and C. laevigatus Vahl. These are surely not related to one another and have in common only the unusual character of petaloid staminate glands. Leandri (1939) noted that the petaloid glands in C. squamigerus appear to be an abnormality and reduced the species to a synonym of C. jennyanus. However, Leandri (1939) also recognized C. lepidotus A. DC. as having petaloid glands, and used that feature as a key character for the species. It seems expedient to try to salvage Müller's name by typifying the section with C. squamigerus so that it can accomodate those Madagascar species with lepidote indumentum, eglandular leaves, and bifid styles.

Representative species:

20. Croton sect. Podostachys (Klotzsch) Baill., Etude Euphorb.: 365. 1858.

Monoecious shrubs; indumentum stellate; leaves alternate, ± palmately veined, dentate, glandular at base; stipules entire; inflorescences terminal, with a distinct gap between staminate and pistillate flowers, without bisexual cymules; petals reduced in pistillate flowers; stamens 5-12; pistillate sessile or pedicellate, sepals entire to laciniate, valvate; styles usually multifid.

This section of c. 10 American species appears to be unnatural as defined by Müller (1873); the species with bidif styles are here assigned to Croton sect. Octolobium. The section is close to C. sect. Geiseleria, and could perhaps be combined with it. In fact, Smith & al. (1988) have proposed treating C. lundianus as a variety of C. glandulosus, in C. sect. Geiseleria!

Representative species:

21. Croton sect. Octolobium Chodat & Hassl. in Bull. Herb. Boissier, ser. 2, 5: 496. 1905.

Monoecious shrubs or subshrubs; indumentum stellate; leaves alternate, palmately veined, glandular at base; stipules entire or nearly so; inflorescences terminal, with a distinct gap between staminate and pistillate flowers, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-15; pistillate flowers sessile or subsessile, sepals 6-8, dentate, valvate; styles bifid to multifid.

It is rather doubful that this section of 2 or 3 South American Species can be maintained as distinct from Croton sect. Podostachys. It is possible that C. mentiens is conspecific with C. aberrans, although from description they differ in stamen number and stylar configurations. Müller (1873) also included 2 other species, C. teucridium Baill. and C. subferrugineus Müll. Arg., in this affinity, but their relationships are doubtful.

Species included:

22. Croton sect. Geiseleria (Klotzsch) Baill., Etude Euphorb.: 359. 1858.

Monoecious herbs or small shrubs; indumentum stellate; leaves alternate, ± palmately veined, dentate, glandular at base; stipules entire; inflorescences terminal, without bisexual cymules, bracts ± glandular; petals reduced in pistillate flowers; stamens 8-11; pistillate flowers sessile or pedicellate, sepals distinctly unequeal, entire, not glandular; styles bifid.

As delimited here, Croton sect. Geiseleria includes c. 10 species of the New World, with most of the diversity in Brazil. Species with multifid styles, larger stamen number, or eglandular leaves are excluded, in contrast to the treatment of Müller (1873). The species show strong resemblances to those in C. sect. Podostachys.

Representative species:

23. Croton sect. Pilinophytum (Klotzsch) A. Gray, Manual, ed. 2: 391. 1856.

Monoecious annual herbs; indumentum of foliage stellate; leaves alternate, ± palmately veined, entire, eglandular at base; stipules entire; inflorescences terminal, contracted, without bisexual cymules; petals reduced in pistillate flowers; stamens 8-15; pistillate flowers subsessile, sepals mostly 7 or 8 (6-10), entire, not glandular; styles multifid.

This is one of the few sections of Croton that is mainly confined to the United States. The 3 species resemble North American species of C. sect. Gynamblosis and sect. Valamea, such as C. leucophyllus and C. lindheimerianus, but differ in having quadrifid rather than bifid styles on the staminate petals. Although differing in its distinctive stellate-lepidote pedicellate trichomes, the South American species C. pycnocephalus Baill. may belong to this section.

Species included:

24. Croton sect. Eremocarpus (Benth.) G.L. Webster in Novon 2: 270. 1992.

Monoecious annual herbs; indumentum bristly-stellate; leaves mostly clustered at forks of dichotomizing stems, entire, palmately veined, eglandular; stipules obsolete; inflorescences pseudoterminal at dichotomies of stems, bisexual; pistillate perianth obsolete, staminate flowers apetalous; stamens 6-10; ovary 1-locular, style unlobed.

This monotypic section, confined to western North America, has been regarded as a distinct genus since soon after Hooker described it (with doubt) as a Croton. The flowers, which are possibly wind-pollinated, are more highly reduced than in any other group of Croton. However, the habit, including pubescence and leaf shape, is highly suggestive of species of C. sect. Pilinophytum and related species of C. sect. Velamea. From an evolutionary point of view, it seems clear to me that Eremocarpus must be regarded as a highly specialized and florally reduced species of Croton.

25. Croton sect. Gynamblosis (Torr.) A. Gray., Manual, ed. 2: 392. 1856.

Monoecious annual or perennial herbs or subshrubs, ± dichotomously branching; indumentum of foliage appressed-stellate or stellate-lepidote; leaves alternate, entire, eglandular; stipules suppressed; inflorescences abbreviated, without bisexual cymules; petals rudimentary of absent in pistillate flowers; stamens 4-11; pistillate flowers distinctly pedicellate, ± reflexed in fruit; sepals narrow, entire, not glandular, valvate; styles bifid.

This American section of 5 species was recognized by Müller on the basis of the asymmetrical staminate flowers. The South American species have not previously been associated with the North American ones, but their resemblance is so close that there can be little doubt they belong here. The plants appear to be reduced forms perhaps derived from within Croton sect. Velamea, and could be accommodated as a subsection within that group.

Species included:

26. Croton sect. Crotonopsis (Michx.) G.L. Webster in Novon 2: 270. 1992.

Monoecious annual herbs; indumentum appressed-stellate and stellate-lepidote; leaves mostly alternate, entire, pinnately veined, eglandular; stipules obsolete; inflorescences pseudoterminal, reduced, usually with a single pistillate flower below the staminate; petals reduced in pistillate flowers; stamens 5 or 6; pistillate flowers sessile, sepals sometimes unequal, entire, not glandular; ovary 1-locular, style multifid; fruit indehiscent, achene-like.

Although I earlier (Webster 1967) followed tradition in recognizing Crotonopsis as a genus distinct from Croton, its close relationship has always been apparent; and it is significant that authors such as Correl & Johnston (1970) have suggested that it could easily be combined. The relationship to such groups as C. sect. Gynamblosis is unmistakable, and it seems significant that there is a reduction series from 3 to 2 carpels within C. sect. Gynamblosis. On the other hand, the indumentum is quite different in the two groups, since the trichomes are distinctly lepidote in Crotonopsis; furthermore, the style in Crotonopsis is multifid, not bifid. The indehiscent fruit in Crotonopsis is rather similar in size and shape to the 2-locular capsule of Croton monanthogynus, and there does not appear to be a great morphological difference. Clearly, Crotonopsis is a highly specialized group derived from taxa within Croton, and it seems quite appropriate to treat it as a section of the latter rather than an independent genus.

Species included:

27. Croton sect. Argyrocroton (Müll. Arg.) G.L. Webster, stat. nov.

Monoecious or dioecious trees or shrubs; indumentum lepidote; leaves alternate, pinnately veined, glandular (rarely eglandular) at base; stipules entire; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-20; pistillate flowers ± pedicellate, sepals entire, eglandular, valvate; styles bifid.

Croton sect. Argyrocroton is poorly represented in the New World, and the bulk of the species appear to be African and Madagascan.

Representative species:

28. Croton sect. Lamprocroton (Müll. Arg.) Pax in Engler & Prantl, Nat. Pflanzen-fam. 3(5): 40. 1890.

Monoecious or dioecious shrubs; indumentum of foliage lepidote at least in part, scales shallowly toothed; leaves alternate, entire, pinnately veined, eglandular; stipules reduced or absent; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-15; pistillate flowers mostly sessile or subsessile, sepals equal to distinctly unequal, entire, eglandular, valvate; styles bifid.

As defined here, Croton sect. Lamprocroton is a South American group of c. 20-30 species (boundaries between species are controversial). The redefined section includes not only the species with bifid styles placed in C. ser. Lamprocroton by Müller (1873), but also the species with bifid styles, eglandular leaves, and shallowly lobed scales in Müller's C. ser. Argyrocroton.

Representative species:

29. Croton sect. Julocroton (Mart.) G.L. Webster in J. Arnold Arbor. 48: 354. 1967.

Monoecious shrubs or herbs; indumentum stellate; leaves alternate, pinnately or palmately veined, entire or dentate, eglandular; stipules entire to laciniate; inflorescences terminal, ± congested, without bisexual cymules; petals reduced in pistillate unequal and ± deeply laciniate; styles bifid or more often multifid.

Although generally treated as a distinct genus, Julocroton does not appear to merit separation unless Croton is divided up into a large number of segregate genera, as Klotzsch attempted to do in the 19th century. Over 50 species of Julocroton have been described, the vast majority from South America, but despite the partial revision of Croizat (1943) the group remains very poorly understood. A general review of geographic distribution patterns in the group is given by Cordeiro (1990), and a provisional enumeration of species accepted by Webster (1992).

Representative species:

30. Croton sect. Adenophyllum Griseb., Fl. Brit. W.I.: 40. 1859.

Monoecious shrubs; indumentum stellate; leaves alternate, palmately veined or triplinerved, with stalked glands on margins; stipules lobed or dissected, ± glandular; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 20-40; pistillate sepals valvate, mostly glandular on margins; styles multifid.

This is an entirely American section of c. 10 closely related species; it is very similar to Croton sect. Barhamia except for the larger stamen number.

Representative species:

31. Croton sect. Barhamia (Klotzsch) Baill., Etude Euphorb.: 367. 1858.

Monoecious shrubs, stems sometimes viscid; indumentum loosely or appressed-stellate, not woodly; leaves alternate, pinnately or palmately veined, usually dentate, without basal glands; stipules ± glandular-lobed or -dissected; inflorescences terminal, elongated, without bisexual cymules; petals reduced in pistillate flowers; stamens (5-)8-12; sepals of pistillate flowers often glandular on back or margins; styles multifid.

Croton sect. Barhamia is entirely American, but unlike C. sect. Adenophyllum it is well represented in South America. The section shows considerable variability: South American species such as C. betulaster Müll. Arg. and C. glutinosus Müll. Arg. are very distinctive in their nearly glabrous, extremely viscid foliage and probably should be segregate in a separate subsection or section. Two other Mesoamerican species, C. brevipes Pax and C. macrodontus Müll. Arg., resemble species of C. sect. Barhamia in habit, but lack clearly glandular-lobed stipules and pistillate calyces; their affinity remains uncertain, but in this synopsis they are tentatively referred to C. sect. Ocalia.

Representative species:

32. Croton sect. Decalobium Müll. Arg. in Linnaea 34: 78. 1865.

Monoecious shrubs; indumentum stellate; leaves alternate, pinnately veined, eglandular at base; stipules glandular-lobed or sometimes nearly entire; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-18; pistillate sepals with stipitate-glandular margins, subtended by and epicalyx of 5 smaller segments; styles multifid.

This small section of 2 species is confined to southern Mexico and Central America. Although the stipules in some specimens of Croton decalobus have the glands highly reduced, the pistillate calyx with copious stalked glands is highly suggestive of that in C. sect. Barhamia. It is possible that a more accurate match of phylogeny to classification would result in demoting C. sect. Decalobium to a subsection of C. sect. Barhamia.

Species included:

33. Croton sect. Micranthis Baill., Etude Euphorb.: 355. 1858.

Monoecious dwarf subshrubs or perennial herbs; indumentum appressed-stellate; leaves alternate, small (less than 1 cm long), pinnately veined, crenulate, blunt, eglandular at base; stipules glandular-lobed; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 5-10; pistillate sepals valvate, ± entire or glandular; styles multifi.

The species of this small American section have a very characteristic habit, but species such as Croton escathos Croizat and C. sect. ovalfolius Vahl represent forms transitional between C. sect. Barhamia and C. sect. Micranthis. It is possible that further study will show that C. sect. Micranthis should be treated as a subsection of C. sect. Barhamia. The distribution of C. sect. Micranthis is curious, with a disjunction between the Greater Antillas and Brazil. The position of C. nanus Urb. & Ekman from Hispaniola remains unsettled; it has the small leaves of C. sect. Micranthis but the woolly indument of C. sect. Medea.

Species included:

34. Croton sect. Medea (Klotzsch) Baill., Etude Euphorb.: 368. 1858.

Monoecious subshrubs or herbs, stems not viscid; indumentum stellate, often woolly; leaves alternate, pinnately or palmately veined, entire or dentate, without basal glands; stipules ± glandular or dissected; inflorescences terminal, contracted, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-12; pistillate flowers sessile or subsessile, sepals laciniate or glandular; styles multifid.

Müller (1873) applied the name Croton ser. Medea to such a large diverse residue of Brazilian species with stellate indumentum that his concept is essentially meaningless. However, in the concept of Baillon that is accepted here, C. sect. Medea is a reasonable well characterized temperate and subtropical South American group of c. 30 named species. The diversity among the species is suggested by the generic synonymy, and further study may result in a rational subdivision of C. sect. Medea into subsections. Some Brazilians species such as C. parvifolius Müll. Arg. and C. parvifolius Müll. Arg. and C. santolinus Baill. have the habit of C. sect. Medea but lack glandular stipules; they may nevertheless be related.

Representative species:

C. schultesii Müll. Arg. is aberrant in its shrubbier habit, suborbicular leaves, and entire pistillate sepals; but it has the glandular stipules and bracts of C. sect. Medea.

35. Croton sect. Lasiogyne (Klotzsch) Baill., Etude Euphorb.: 370. 1858.

Monoecious trees or shrubs; indumentum stellate (or partly stellate-lepidote); leaves alternate, pinnately or palmately veined, minutely denticulate, glandular or eglandular at base; stipules usually entire, sometimes foliaceous; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 15-20; pistillate flowers pedicellate, sepals reduplicate-valvate, entire, not glandular; styles multifid.

In the sense of Müller (1866, 1873), Croton subsect. Lasiogyne included all species of Croton with reduplicate-valvate calyces in the pistillate flowers. Here C. sect. Lasiogyne is constructed more narrowly in the sense of Klotzsch and of Baillon, to include c. 25 species widely dispersed in the New World. Despite its lower stamen number and entire stipules, C. santaritensis appears to belong here because of its resemblance to C. fragans.

Representative species:

36. Croton sect. Argyroglossum Baill. in Adansonia 4: 289. 1864.

Monoecious trees or shrubs; indumentum lepidote; leaves alternate, pinnately or palmately veined, ± entire, not glandular at base; stipules not glandular; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-15; pistillate flowers pedicellate, sepals reduplicate-valvate, entire, not glandular; styles multifid.

As defined here, Croton sect. Argyroglossum has a narrower circumscription than that of C. ser. Argyroglossum of Müller (1873), as it excludes species with glandular stipules or calyces. The section appears to be entirely American, with a total of c. 15 species. C. sellowii Baill. is anomalous in having lepidote indumentum and reduplicate-valvate pistillate sepals as in C. sect. Argyroglossum but glandular-dissected stipules as in C. sect. Codonocalyx; its position must be regarded as uncertain.

Representative species:

37. Croton sect. Astraeopsis Baill., Etude Euphorb.: 362. 1858.

Monoecious shrubs; indumentum appressed-stellate, sparse; leaves alternate, pinnately veined, entire, eglandular at base; stipules glandular-lobed; inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-12; pistillate sepals reduplicate-valvate, ± glandular-dentate; styles multifid.

Croton sect. Astraeopsis is confined to North America and is largely a Caribbean group, with less than 5 species. C. guyanensis Aubl., which was cited under C. sect. Astraeopsis by Müller (1866), differs in its glandular quintuplinerved leaves and does not appear to be closely related to C. lucidus. Despite its non-reduplicates sepals, it is possible that C. soliman Schltdl. & Cham. may be related to species in this section.

Representative species:

38. Croton sect. Codonocalyx Klotzsch ex Baill., Etude Euphorb.: 369. 1858.

Monoecious or dioecious subshrubs or perennial herbs; indumentum stellate or stellate-lepidote, densely tomentose or loosely stellate-lepidote; leaves alternate, pinnately veined, entire, eglandular at base; stipules ± glandular-lobed (sometimes ± obsolete); inflorescences terminal, without bisexual cymules; petals reduced in pistillate flowers; stamens 10-15; pistillate flowers pedicellate, sepals reduplicate-valvate, entire or dentate; styles multifid.

Croton sect. Codonocalyx, which is confined to temperate and subtropical South America, includes about 10-12 species. The section is variable, and the type of C. sect. Calycireduplicati differs from the type of C. sect. Codonocalyx in being dioecious rather than monoecious and in having dentate than entire pistillate sepals. However, there are transitional species such as C. helichrysum that are monoecious but have dentate pistillate sepals. Perhaps C. sect. Calycireduplicatae can be retained at subsectional rank. Allen (1978) has reduced many of the proposed names to C. montevidensis. A species from Bolivia, C. avulsus Croizat, although lacking glandular stipules and reduplicate-valvate pistillate calyx, may represent a specialized member of this section.

Representative species:

39. Croton sect. Astraea (Klotzsch) Baill., Etude Euphorb.: 363. 1858.

Monoecious shrubs or herbs; indumentum stellate, often sparse; leaves alternate, mostly palmately veined or lobed, glandular at base; stipules mostly entire, sometimes glandular or reduced; inflorescences terminal, with or without bisexual cymules; floral receptacle nearly or quite glabrous; petals reduced in pistillate flowers; stamens 12-15; pistillate flowers pedicellate, sepals entire or denticulate; styles mostly multifid; seeds cylindric-tetragonous.

This American section of c. 10 species is one of the more sharply defined within the genus. However, the status of the common weedy species C. bonplandianus Baill. (treated as C. pauperulus by Müller) is doubtful. It differs in its prominent basal foliar glands, bifid styles, and smooth seeds; possibly it has independently lost the receptacular indumentum characteristic of C. sect. Astraea.

Representative species:

40. Croton sect. Drepadenium (Raf.) Müll. Arg. in Linnaea 34: 79. 1865.

Monoecious or dioecious subshrubs or herbs; indumentum appressed-stellate or stellate-lepidote; leaves alternate, entire, pinnately veined, eglandular at base; stipules rudimentary or absent; inflorescences terminal, mostly unisexual; petals absent in both staminate and pistillate flowers; stamens 8-12; pistillate flowers ± pedicellate, sepals entire, eglandular, valvate; styles multifid.

All students of Croton have recognized this well-defined section that includes 5 or 6 species of North America and the Caribbean. The species recognized by Müller (1866) have not all been accepted by later workers.

Representative species: