|
Go to last lab (Bellflowers) Go to next lab (Orchids) 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.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 lato, i.e. the Cronquistian Liliaceae)
NOTE ! The family has been broken into many segregates on molecular grounds. We will make no discussion of these segregates below except insofar as they are helpful to know for identification.
Diagnostic family characters
Leaves: Simple, entire, alternate, less often whorled or opposite, cauline or in basal rosettes, parallel veined. Generally sessile, though some genera (e.g. Trillium) have net-like venation and +/- petiolate leaves.
Flowers: Actinomorphic, hypogynous (except where combined with the Amarylidaceae, which is distinguished by inferior ovaries; two local genera in the Liliaceae, Aletris and Zigadenus are apparently 1/2 inferior), often but not always reduced. Perianth composed of 6 tepals in 2 cycles, the outer green and sepaloid, the inner 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.
SPECIES TO LEARN:
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. Clintonia borealis (Liliaceae) 'Yellow bead-lily,' 'Bluebead lily'
This ubiquitous herb of the northwoods forest floor has yellow flowers and bright round blue fruits -- hence the two common names. It is more common in wet forests -- for some reason I always associate it with getting bit by mosquitoes. The fruits are allegedly mildly toxic. The genus is named after a New York politician from the early 1800's. In WI it is found throughout the state but more commonly up north.
155. Trillium grandiflorum ("Liliaceae") 'Big white trillium,' 'Large-flowered trillium'
Trillia are very simple in structure: each plant consists of an underground rhizome that gives rise to individual flowering stems (peduncles) to each of which are attached three leaves. Technically, these leaves 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 placed in the lilioid family Melanthiaceae.
156. Maianthemum canadense ("Liliaceae") '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.GENERA TO LEARN:
157. Uvularia ("Liliaceae" or now Colchicaceae) '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.
158. Lemna (Lemnaceae or now Araceae) 'Duck weed'
Although you may not have realized it you have probably seen this plant many times. It is the diminutive little green plant found floating on almost all of Wisconsin's waterways. The most common species, Lemna minor, consists of a flat, oval-shaped thallus, sometimes called a frond, with a single little root dangling in the water. Another common species, L. trisulca, has a forked or branching habit and tends to float a little below the water's surface. Although Lemna does rarely produce flowers and seeds it primarily reproduces by budding. Some claim that they are the fastest-growing higher plants; they can double their mass in as little as 24 hours. The species and its relatives (Wolffia, Wolffiella, and Spirodela) are eaten by both ducks and fish. The duckweed family is now placed within Araceae.
Take a few pieces from the bowl in a petri dish and look at them both top and bottom under a scope. Also look at the flowers of Pistia (a floating aquatic in Araceae) under the microscope up front.
159. Sagittaria (Alismataceae) 'Arrow head'
Both the common and scientific name of this aquatic plant come from the characteristic shape of the leaves (they are sagittate). The leaves are all basal with petioles typically as long as the water is deep. In some species the leaves are emergent. Often, when leaves are completely underwater they will be ribbon-shaped. The entire family typically produces unisexual white flowers which can be either above ( or perhaps rarely) beneath the water's surface. ** Check out the live plant next to the herbarium specimen.
160.Potamogeton (Potamogetonaceae) 'pondweed'
These are aquatics, many with floating leaves and all with submerged leaves (that quickly rot away in many floating-leaved species). Many species produce terrestrial forms when needed -- these vary markedly from the aquatic forms. The leaves are arallel veined with prominent stipules. Flowers are small, inconspicuous, and wind-pollinated. In general, the genus is highly plastic, changing with differing environmental conditions, making the species difficult to key out.
