Lab 17: Bellflowers, Asters, and Goldenrods

 

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Both the Campanulaceae and the Asteraceae exhibit a unique mechanism of pollen presentation. The anthers are fused or coherent to form a tube into which they dehisce. When the style elongates, the pollen collects on hairs on its outer surface. This pollen is in turn collected by bees before the stigmas become receptive. The stigmas then unfurl and become receptive to pollen. Sometimes the stigmas unfurl so far that they contact the dusting of pollen on the style, effecting a self-pollination. ** Look for this characteristic arrangement of androecium and gynoecium when you are dissecting flowers today.

141 & 142. Campanulaceae, the Bellflower family (includes the traditional Lobeliaceae)
Diagnostic family characters
Leaves: Simple, alternate, no stipules.
Milky latex generally present.
Flowers: Actinomorphic (in the Campanuloideae subfamily) dor zygomorphic (in the Lobelioideae, which = the traditional Lobeliaceae), usually perfect, mostly epigynous, with nectariferous disc, sometimes resupinate (pedicel twisted 180 degrees, making the flower "upside down.")
Fruits: Mostly capsules, sometimes a berry, seeds numerous, small; endosperm copious, fleshy, and oily.
Habit: Annual or perennial, mostly herbs, sometimes shrubs.

Key out species 141 (Campanulaceae): Campanula rapunculoides 'Creeping bellflower,' 'European bellflower'
This showy plant is still used in gardens despite its invasive nature. The blue, bell-shaped flowers are common in this family. Despite its common name, this is an upright-growing plant with the flowers borne along the top of the stem.

Key out species 142 (Campanulaceae): Lobelia siphilitica 'Great blue lobelia'
The beautiful blue flowers bloom from August to September, they are borne on 2 to 3 foot stalks.

 

143 to 150. Asteraceae, the Aster, Composite, or Sunflower family (= Compositae)
Diagnostic family characters

Tribe Heliantheae

Tribe Astereae (5 genera in Wisconsin)
Like Heliantheae, but:

Tribe Senecioneae (4 genera in Wisconsin)
Like Heliantheae, but:

Tribe Anthemideae (7 genera in Wisconsin)
Like Heliantheae, but:

Tribe Lactuceae (12 genera in Wisconsin)

 

Key out species 143: Achillea millefolium 'Common yarrow.' Tribe: Anthemideae

Widespread species with distinctive lacy leaves and radiate heads. A pink headed variant exists here as well.


SPECIES TO LEARN:

144. Coreopsis palmata (Asteraceae: Heliantheae) 'Prairie tickseed,' 'Prairie coreopsis'

Prairie tickseed is one of our native yellow composites with radiate heads. It is a distinctive plant common in prairies and savannas. The leaves are opposite and tri-lobed. The pappus is reduced to two tiny teeth. The four species of Coreopsis in Wisconsin are closely related to the genus Bidens – the beggar’s-ticks – species that have a pappus comprised of 2 distinct barbed awns.


145.
Symphyotrichum novae-angliae (formerly Aster novae-angliae, Asteraceae: Astereae) 'New England aster'
Compared to other native asters, New England Aster has the most intense purple flowers and the most rays (about 40). It can be differentiated from other asters by the conspicuous lobes (auricles) at the base of the leaves that clasp the softly-hairy stem. Often cultivated. In the near future, all of our asters will be transferred to other, new genera because they are not related to each other nor to the type species of the genus Aster, the Italian aster from Europe.


146. Packera paupercula (Asteraceae: Senecioneae) 'Balsam ragwort'
(formerly Senecio pauperculus)
This genus has been subdivided based on chromosomal study. The two genera are Packera and Senecio:

  1. Leaves +/- equal in size up the stem; annuals (perhaps rarely biennials)...........................Senecio
  2. Cauline leaves progressively reduced in size up the stem and lobed (unlike the basal leaves);
    Perennials (rarely monocarpic), usually with obvious asexual reproduction.................. Packera


147. Hieracium aurantiacum (Asteraceae: Lactuceae) 'Orange hawkweed'
A weedy, pretty, and taxonomically challenging genus. The hawkweeds are notorious for hybridization and agamospermy (the assexual production of seed). The result is a slew of "microspecies" that are geographically restricted, morphologically similar, and all but impossible to distinguish from one another.

GENERA TO LEARN:

148. Antennaria (Asteraceae: Gnaphalieae) 'Pussy-toes'
Antennaria is one of the more commonly encountered spring flowering members of the Asteraceae in Wisconsin. There are five species of Antennaria in Wisconsin, although several subspecies are also currently recognized. Look for these low-growing species in open sites such as prairies, old fields, and even lawns.

149. Helianthus (Asteraceae: Heliantheae) 'Sunflower'
Many hybrids in this genus. Watch out for look-alikes in Heliopsis, Silphium, and Rudbeckia.

150. Solidago (Asteraceae: Astereae) 'Goldenrod'
Hybrids are common. Members of the Canada goldenrod complex almost invariably have stem galls. Like Aster, the genus is easily recognized but the species can be difficult to differentiate.