Lab 18: Arums, Lilies, and Orchids


Go to last lab (Bellflowers) Go to next lab (Graminoids) Go to lab syllabus


151. Araceae, the Arum family
Diagnostic family characters
Leaves:. Simple to pinnately or palmately compound, entire. Alternate, basally clustered (basal lvs each with a sheathing petiole), or cauline. Leaves tend to be broad and in some species (e.g. Arisaema, Symplocarpus) the veins form a sort of margin around the edge of the leaf.
Inflorescence: A very characteristic spadix (cylindrical, fleshy axis packed with numerous small, ebracteate flowers) and spathe (large, foliose or petaloid bract +/- surrounding the spadix).
Fruits: Berry.
Habit: Rhizomatous or tuberous perennial herbs, or tiny(!) floating aquatics of former Lemnaceae.

WATCH OUT! This family has bundles of needle-like calcium oxalate crystals (raphides) that can cause painful injury to the mouth and throat. Hospitals see many children each summer who have eaten the bright red berries produced by species #151. Take a look at the display case in the entrance to Birge Hall for an exhibit about the largest arum of them all, the Amorphophallus titanum.

Key out species 151: Arisaema triphyllum 'Jack-in-the-pulpit'
This is a forest species, common in oak and maple woods throughout Wisconsin. Easy to confuse with either poison ivy or trillium before it blooms. Related to a really fancy floodplain forest species named green dragon.


152. Liliaceae, the Lily family (sensu stricto)
NOTE ! The Liliaceae is used in the narrow sense here. Older manuals (e.g., Gleason&Cronquist; Wisconsin Flora) and websites (e.g., Wisflora) use Liliaceae in the broad sense to include many unrelated genera. Unfortunately, Field Manual of Michigan Flora (and their website) breaks up the petaloid monocots into smaller families incorrectly. The Student Herbarium has the correct families and should be checked. Please see the petaloid monocot handout from lecture that lists these different families and how different sources place each petaloid monocot genus.

Diagnostic family characters
Leaves: Simple, entire, alternate, less often whorled or opposite, cauline or in basal rosettes, parallel veined. Generally sessile.
Flowers: Actinomorphic, hypogynous. Perianth composed of 6 tepals in 2 cycles, usually all petaloid. 3-carpellate superior ovary with axile placentation.
Fruits: Usually a loculicidal capsule, seldom a berry, typically with flat seeds.
Habit: Perennial herbs with bulbs or rhizomes; showy flowers on terminal inflorescences.

Recognize this family on site in the field by the annual, strap or ribbon-like leaves, or in some genera more ovate leaves with prominent parallel veins that follow the leaf margin (reminiscent of dicotyledonous arcuate veins). The leaves often have a glossy appearance and are invariably entire. The flowers are also distinctive: three-merous, perianth parts unfused, flowers often pungent.

Key out species 152: Erythronium albidum 'White trout lily'
This small, colonial lily gets its common name from the mottled appearance of the leaves. It is a spring ephemeral, meaning that it flowers, sets seed, and senesces before the leaves are fully unfurled in the canopy above. Like several spring ephemerals, there is a corresponding northern Wisconsin member in this genus: Erythronium americanum, 'yellow trout-lily.' Both of these species are also referred to as dog-tooth violets, the dog-tooth perhaps refering to the shape of the rhizome.


153. Symplocarpus foetidus (Araceae) 'Skunk cabbage'
This is the first native plant to come into bloom in Wisconsin, in early spring. The spadix generates heat that allows the inflorescence (surrounded by the spathe) to melt any remaining snow, so it emerges before any other plants are out. The heat also volatilizes chemicals that attract insects (like flies) that will pollinate the flowers. This species gets its common name from its leaves, which resemble large cabbage leaves and flourish after the inflorescence has died back. Its distinct smell resembles that of native striped mammal Mephitis mephitis.


154. Trillium grandiflorum (Melanthiaceae, former "Liliaceae", Trilliaceae in MICH) 'Big white trillium,' 'Large-flowered trillium'
Trilliums are very simple in structure: each plant consists of an underground rhizome that gives rise to individual flowering stems (peduncles) to which are attached three lvs. Technically, these lvs are bracts; peduncles don’t have true leaves. The large, showy, white petals of this species turn pinkish with age. Trillium has traditionally been placed in the Liliaceae, but recently it has been moved to the lilioid family Melanthiaceae.

155. Maianthemum canadense (Asparagaceae, former "Liliaceae", Convallariaceae in MICH) 'Canada mayflower,' 'Wild lily of the valley,' 'False lily of the valley'
Although small (3"-8"), this perennial, rhizomatous herb is one of the dominant understory species of the northwoods. It can have from one to three leaves. It produces small but showy, white, insect pollinated flowers that ripen into little berries. It does not reproduce well by seed but the rhizomes are effective vegetative reproductive organs. A single clone can be up to 20 feet in diameter and can be as old as 60 yrs. A larger Eurasian species, Convallaria majalis, looks like Maianthemum and also goes by the common name 'Lily-of-the-valley' -- but this "true" Lily of the valley is an ecologically invasive weed, a pest in oak savannas and woodland edges. Both genera are now placed in the lilioid family Convallariaceae. Once part of the Liliaceae sensu lato, both genera are now placed in Asparagaceae, although Field Manual of Michigan Flora erroneously places them in Convallariaceae..


156. Uvularia (Colchicaceae, former "Liliaceae", Convallariaceae in MICH) 'Bellwort' 'Merrybell'
Two species occur in our rich deciduous woodlands and commonly seen in spring. The plants have sessile or perfoliate leaves on a somewhat ‘drooping’ stem. The somewhat closed, bright yellow to cream-colored flowers with twisted tepals give rise to triangular capsules later in early summer. The genus is now placed in the family Colchicaceae.

157. Sagittaria (Alismataceae) 'Arrow head'
Both the common and scientific names of this aquatic plant come from the characteristic shape of the lvs (they are sagittate). The lvs are all basal with petioles typically as long as the water is deep. In some species the lvs are emergent. Often, when lvs are completely underwater they will be ribbon-shaped (as is the case with some of our specimens). The entire family typically produces unisexual white flowers which can be either above, or perhaps rarely, beneath the water’s surface.

158. Iris ‘Northern blue-flag,’ ‘Blue iris’

Blue or yellow flowered species are common in swamps and low ground throughout eastern and central North America. Superficially, the leaves can look like those of cattail (Typha). Cattail leaves, though, are curved at the base to wrap around a central axis. They can also resemble the leaves of Acorus (Acoraceae: sweet flag), though the latter is strongly scented. The floral structure of Iris is unique in our flora. The perianth is modified into an outer, spreading whorl of tepals called falls and an inner whorl of erect tepals that are called standards. Curving over the top of each fall is a petaloid style. Sandwiched between the style and the fall is a stamen.

159. Sisyrinchium 'Prairie blue-eyed grass.'
Although grass-like vegetatively, this genus of wet to dry loving species has petaloid blue or white flowers. Smaller than those in Iris, the flowers are subtended by spathe bracts. Most species are small perennials that bloom in the late spring and early summer.

160. Goodyera (Orchidaceae) 'Rattlesnake plantain'
The 4 to 8 oblong-elliptical leaves, which form a basal rosette, somewhat resemble plantain (Plantago) leaves--hence the common name. This plant is typically found in dry upland oak or pine woods. It has been frequently observed growing out of clumps of moss. It is perhaps the most common native orchid in southern WI.