PONIEDERIACEAE (PICKEREL-WEED FAMILY) 51 



ARA.CEAE (Arum Family) 



Herbs, perennial, large. Leaves large, simple. Flowers crowded 

 on a spadix; spalhe surrounding spadix, usually conspicuous. 

 Perianth of 4 or 6 green sepals. Stamens 4 or 6, opposite the 

 sepals. Fruit usually berry-like. 



A. Leaves 7-45 cm. wide, netted-veined, with skunklike smell; spathe yellow. 

 W. C. E. — (Gk. lysis = a loosening, chiton = a mantle; referring to the loosening 

 spathe.) Lysichlton camtschatcense (skunk cabbage) 



AA. Leaves 2.5 cm. or less wide, parallel-veined, without skunklike smell; spathe 

 green. E. — Rhizome medicinal. (The ancient name.) 



Acorus calamus (sweet flag) 



LEMNACEAE (Duckweed Family) 



Minute, stemless, floating, merely i or more flattened or spherical 

 multicellular green bodies either with roots hanging from the 

 under side or without them. Flowers extremely rare. Fruit a 

 utricle. — Floating on ponds or lakes. 



A. Thalloid shoots 1-5-veined, with o-i rootlet; rootlets without vascular tissue. 



LEMNA (p. si) 



AA. Thalloid shoots 7-is-veined, with 2-10 rootlets; rootlets with central vascular 

 cylinder. W. E. — (Gk. spira = a cord, delos = evident; from the threadlike 

 roots.) Spixodela polyrbiza (large duckweed) 



LEMNA (Duckweed) 



ThaUoid shoots with many needle-shaped crystals in the cells. — (Gk. 

 Hmne = a swamp ; referring to the habitat.) 



A. Thalloid shoots loag-stalked at base, broadly oar-shaped, 6-10 mm. long, 12 or 

 fewer connected. L. trisulca (fairy paddle) 



AA. Thalloid shoots sessile, elliptic-oblong, 2.5-4 mm. long, s or fewer connected. 



L. minor (small duckweed) 



PONTEDERIACEAE (Pickerel-weed Family) 



Herbs, low; stems creeping or ascending or floating. Leaves 

 grasslike. Flowers subtended by a leaflike spathe, perfect, mostly 

 irregular; solitary, small, yellow. Perianth free from the ovary, 

 corolla-like, 6-parted; segments linear; tube threadlike. Stamens 

 3, unequal, on the tube. Ovary fusiform; style i; stigma 3-lobed. 

 Fruit a many-seeded capsule. — E. In water or bogs. (Gk. hetera = 

 different, anthera = anther ; ours and some other species have 2 forms 

 of anthers.) Heteranthera dubia (mud plantain) 



