Lab 15: Mints and Snapdragons

 

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121. Lamiaceae, the Mint family (=Labiatae)
Diagnostic family characters
Leaves:. Variable; usually serrate, almost always opposite, without stipules.
Stems: Generally square. The combination of opposite leaves and square stems is almost unique to mints ­ the family Verbenaceae has some members that show this combination, as do some members of Urtica.
Flowers: Usually zygomorphic, perfect, hypogynous, bilabiate sympetalous corolla. This family is unique in having styles that are gynobasic, meaning that each flower has its style arising from a depression in the ovary. Make sure to look for this in the flower you dissect.
Fruits: 2-locular but appearing 4-locular due to ovary wall intrusions (false septa)
Habit: Many species are aromatic, especially when crushed. In Wisconsin, only herbs

Key out species 121: Nepeta cataria 'Catnip'
This is a weedy species commonly found in lawns and garden beds.

122. Orobanchaceae, the Broomrape family
Diagnostic family characters
Leaves: Simple, sometimes scale-like, without stipules.
Flowers: Zygomorphic, perfect, hypogynous.
Fruits: Usually a septicidal capsule (a capsule that splits along the partitions between the locules), many small seeds.
Habit: Herbaceous to shrubby plants. On most species the flowers are quite attractive. Varying from hemiparasites (green) to obligate parasites (non-green).

The hemiparasitic members of this family were once placed in the snapdragon family, Scrophulariaceae, whereas the holoparasitic members were confined to Orobanchaceae. This family can be confused with the Lamiaceae based on its bilabiate flowers, which are highly variable in shape and color. The flowers in many species are more nearly actinomorphic than is generally the case in the mints. Moreover, the figworts lack the square stem and uniformly opposite leaves of the Lamiaceae. Many genera in the family are hemiparasitic.

Key out species 122: Pedicularis canadensis 'Lousewort,' 'Betony'

123. Oleaceae, the olive family
Diagnostic family characters
Leaves: Simple or (in one of our genera) pinnately compound, opposite, no stipules.
Flowers: Actinomorphic, hypogynous, reduced (small).
Fruits: A drupe, loculicidal capsule, or samara. The samaras are reminiscent of maple fruits, except that in Fraxinus the fruits are not found in pairs, as they are in Acer.
Habit: Shrubs or trees. Our only genus of trees with opposite, pinnately compound leaves is found in this family.

Key out species 123: Fraxinus pennsylvanica 'Green ash' 'Red ash'

SPECIES TO LEARN:

124. Monarda fistulosa (Lamiaceae) 'Wild bergamot'
This showy mint is common in all types of prairies (except the driest) throughout the state and is often found along highways in large patches. The opposite leaves, square stems, and aromatic nature of the plant immediately tell you it is a mint. Wild bergamot was considered a medicinal plant by many Native Americans including the Menominee, the Ojibwe, and the Winnebago (Ho-Chunk). It was used most commonly to treat colds, and was frequently made into a tea.

125. Catalpa speciosa (Bignoniaceae) 'Northern catalpa'
This is a predominantly tropical family, with some species getting into the temperate zone. Northern Catalpa is native to the U.S., but not as far north as Wisconsin here it is found only as a planted tree or an escapee from cultivation. Recognize it by the leaf shape (huge, often with cordate bases) and the fruits, which are somewhat obscenely reminiscent of green beans. In fact, these "beans" are not legumes at all, but rather capsules (arising from a 2-carpellate pistil ­ recall that legumes arise from single, unfused carpels). It has been said by some, particularly juveniles, that the dried fruits can be smoked-much like cigars-this is most definitely not recommended though. Many members of the family, especially in the tropics, are vines (lianas).

126. Castilleja coccinea (Orobanchaceae, former Scrophulariaceae) 'Indian paint-brush'
A hemiparasitic species. The flowers are small and surrounded by larger, showy 2 or 3-lobed bracts. Although ‘coccinea’ means scarlet in Latin, the species has both red and yellow variants. This is our most widespread species of the genus – most species inhabit the Rockies down through the higher elevations of the Andes.

GENERA TO LEARN:

127.Verbena (Verbenaceae) 'Vervain'
This is one of several genera in the Verbenaceae that have opposite leaves and square stems, as we find in the Lamiaceae. Many (though not all) species in this genus are hairy, and the elongate floral spikes (which bloom acropetally, that is from bottom to top) are distinctive.

128. Plantago (Plantaginaceae) 'Plantain'
This is a genus of tramps, many adventive from other countries and now all but cosmopolitan. The species are predominantly found in disturbed habitats such as lawns, cliffs, riverbanks and sand barrens. The genus is distinguished by its rosettes of basal leaves (except in one species, Plantago psyllium) and spikelike, scapose inflorescences well suited for wind pollination. Another common name applied is ‘White man’s footsteps’ in reference to how the plants were brought along by European settlers. Rubbing a crushed Plantago leaf on a mosquito bite may relieve the itching.

129. Conopholis (Orobanchaceae) 'Squawroot'
The plant is parasitic, generally on oak trees, and as a consequence does not depend on photosynthesis. The plant is pale and unique in habit, forming clusters on forest floors. There is an abundance of squawroot in red oak stands in the Baraboo Hills (see map). Keep your eyes peeled for this one. Does this genus remind you of Monotropa?

130. Utricularia (Lentibulariaceae) 'Bladderwort'
Common bladderwort, U. vulgaris, can be found in lakes throughout the glaciated portion of the state. Our other species are more fussy about habitat and restricted in range. They are all carnivores with specialized bladders that open and engulf aquatic organisms. The genus is interesting among aquatic plants in that (1) it possesses some members that live in solid substrates, as emergent aquatics, along with others that live a submergent existence; and (2) the submerged species do not root in the substrate. It is also somewhat anomalous among carnivorous plants in that it tends to produce more bladders in richer environments than in more nutrient-limited environments. The underwater vegetation of this plant looks a lot like Ceratophyllum—which you have already learned.