Arum Family (Araceae) A unique characteristic of this family is the elaborate reproductive structure consisting of a fleshy spike of flowers, the spadix, subtended by a leaf-like bract, the spathe. These mostly tropical and subtropical plants are usually terrestrial herbs growing on the forest floor. Because of their low-light tolerance, they are popular as houseplants in cool climates. Poisonous calcium oxalate crystals are present in plant tissues and there may be a milky sap (latex). The leaves are simple or compound, occur at the base or are alternate on the stem, and have petiole bases that sheath the stem. The small flowers on the spadix are bisexual or unisexual. The flowers have an odor of rotten flesh, which attracts fly pollinators (see 34). There are 1 to 6 stamens and a single pistil with one to many carpels. Sepals and petals that look alike (tepals) may be present. The fruit type is a berry. There are about 110 genera and about 2,000 species. Of interest . . . ornamentals: Aglaonema (Chinese evergreen), Amorphophallus (voodoo lily), Anthurium (flamingo flower), Caladium (elephant’s-ear), Dieffenbachia (dumb-cane), Helicodicerus, Monstera deliciosa (Swiss-cheese plant, cut-leaf philodendron), Philodendron, Pistia (water lettuce), Scindapsis (pothos, devil’s-ivy), Spathiphyllum (flame plant), Zantedeschia aethiopica (calla lily); food: Alocasia (taro), Colocasia (taro), Xanthosoma (tannia); native wild plants: Arisaema triphyllum (Jack-in-the-pulpit), Calla palustris (wild calla), Orontium (golden club), Peltandra (arrow arum), Symplocarpus foetidus (skunk cabbage, see 34). As skunk cabbage shoots develop in early spring in northern temperate regions, they melt the snow around each shoot. This heat is generated through high
respiration rates in the developing spadix, in sufficient amounts to melt the snow and ice. Spathiphyllum
Flame Plant
This perennial herb has simple leaf blades (a) with sheathing petioles (b). The spadix (c) of bisexual flowers is subtended by a white petal-like spathe (d). Each flower (e) has 6 tepals (f) enclosing 6 stamens. The anther (g) of the stamen is shed form a fleshy filament (h) after pollen is released. The pistil (i) has a flattened 3-part stigma (j) with ovules (k) in basal placentation (see 28). Arisaema triphyllum
Jack-in-the-pulpit
This North American wild flower is a perennial herb that arises from a solid bulb-like structure (corm, see 12). The compound leaf blade (l) is divided into 3 leaflets (hence, triphyllum). The petiole (m) is enclosed by a sheath (n) at the base. Plants with one compound leaf have male flowers on the spadix, while plants with two compound leaves have female flowers. This unusual plant has unisexual flowers on the same plant at different times. Young plants with one compound leaf have only male flowers at the base of the spadix. In subsequent years, two leaves develop from the corm, and in a developmental sex change, the spadix produces only female flowers. Energy is expended in the production of fruit; so food produced in the leaves and translocated to the corm must be sufficient to assure that shoot and reproductive (flowering and fruiting) development occurs the following year. In autumn, on plants with female flowers, a cluster of red berries (s) is revealed as the spathe and leaves (t) wither.
COLOR CODE green:
blades (a), petioles (b, m), leaflets (l), sheath (n) white: spadix (c), spathe (d), tepals (f), pistil (i), stigma (j), ovules (k), filaments (h) yellow: anthers (g) light green: outer spathe (o), spadix (q), peduncle (r) purple: inner spathe (p) red: berries (s) tan: peduncle (u), leaves (t) 127