ARUM FAMILY 143 



Family 14. ARACEAE. Arum Family. 



Fleshy, perennial, mostly acaulesccnt herbs, with rootstocks. Leaves 

 b:i.sal, usuall}^ petioled, with broad, simple or rarely divided, reticulate- 

 vciued blades, or narrowly linear with sheathing bases. Flowers perfect, 

 monoecious or dioecious, borne in a dense fleshy spike (spadix); this sub- 

 tended by or enclosed in a large foliaceous or colored bract (spathe). Peri- 

 anth of scale-like members or wanting. Stamens 4-10, with very short 

 filaments and thick connectives. Gynoecium of a single carpel or of several 

 united carpels. Ovaries 1-several-celled; stigmas terminal; ovules 1 to 

 several in each cavity. Fruit a berry or a utricle. 



Spadix terminal, with an oblong sheathing spathe; leaves petioled, with broad blades. 



1. Lyskhiton. 

 Spadix borne somewhat laterally on the leaf-like scape; spathe leaf-like, continuous to 

 the scape; leaves narrowly linear, equitant. 2. AcoRUS. 



1. LYSiCHITON Schott. Skunk Cabbage. 



Acaulescent perennial swamp plants, with short thick rootstocks. Leaves 

 fleshy, petioled, with sheathing bases, the earlier reduced to merely inflated 

 sheaths. Spathe sheathing at the base. Spadix cylindric, at last long-exserted. 

 Flowers perfect, crowded. Perianth 4-lobed. Stamens 4, opposite. Pistil 

 solitary; ovarj' 2-celled, 2-o\'uled; stigma depressed. Ovules horizontal, ortho- 

 tropous. P'ruit fleshy. 



1. L. kamtschatcensis Schott. Leaf-blades 3-7 dm. long, 7-25 cm. 

 broad, elliptic to lance-oblong, acute at both ends; spathe oblong-lanceolate, 

 1-1.5 dm. long; peduncles 15-30 cm. long; spadix 7-12 cm. long, becoming 5-6 

 cm. thick. Swamps: Alaska — ^Mont.- — -CaUf.; e Asia. Submont. Aly-Je. 



2. ACORUS L. Sweet Flag, Calamus-root. 



Erect swamp plants, with long horizontal rootstocks. Leaves sword-shaped, 

 equitant. Scapes 3-angled, bearing a lateral spadix and a foliaceous spathe, 

 continuous with the scape. Plowers perfect, densely crowded on the spadix. 

 Perianth with 6 membranous concave divisions. Stamens 6. Pistil solitary; 

 ovary 2-4-celled, each 2-8-ovuled; stigma depressed-capitate. Fruit berry-hke. 



1. A. Calamus L. Leaves linear, erect, 5-20 dm. long, 1-2 cm. wide, long- 

 a,ttenuate, 2-ranked; scape 1-2 m. high; spathe 2-7.5 dm. long; spadix 5-7 cm. 

 long, about 1 cm. thick, lance-cyUndric; plant seldom fruiting. Swamps and 

 streams: N.S. — -Fla. — Tex. — Colo. — Ida. — -Mont.; Eurasia. Plain. My-Jl. 



Family 15. LEMNACEAE. Duckweed Family. 



Minute floating perennial acjuatics, consisting of a fleshy or membran- 

 aceous, loosely cellular thallus-like stem, without leaves and in our genera 

 with one or more rootlets. The new stems or fronds are produced from two 

 lateral depressions or pouches or a terminal one; the new frond being attached 

 to the old one by a short, slender stalk, soon separating. Flowers very 

 Tare. Inflorescence consisting of 1 pistillate and 1 or 2 staminate flowers, 

 borne on the edge on the upi)er surface of the frond. Staminate flower of 

 a single stamen, with 2-4 pollen-sacks. Pistillate flowers of a single flask- 

 like pistil, with 1-several ovules. Fruit a 1-6-seeded utricle. 



Kootlets solitary, without a fibro- vascular bundle. 1. Lemna. 



Rootlets several, each with a fibro- vascular bundle. 2. Spirodela. 



1. LEMNA L. Duckweed. 



Frond disk-hke, 1-5-nerved or nerveless. Stipe attached to the basal mar- 

 gins of the frond. Rootlet soUtary, without fibro-vascular bundles. Anthers 

 dehiscent transversely. 



