244 ABACEAE LEMNACEAE 



ARACEAE. ARUM FAMILY. 



Perennial glabrous herbs with large leaves, perfect or usually unisexual 

 flowers crowded on a spadix surrounded by a usually colored spathe. Ovary 1 

 to several-celled, ovules 1 to several in each cell. Genera 105 and species 900, 

 mostly tropical, a few in the temperate zones. 



Bibliog. Engler, A., Araceae (DC. Monog. Phan. 2:1-681, 1879). 



1. LYSICHITON Schott. 



Peduncle and basal leaves from a stout rootstock. Flowers perfect, the calyx 

 4-lobed with 4 stamens opposite the segments. Ovary 2-celled, 1 ovule in each 

 cell; stigma depressed. Fruit a 2-seeded berry sunk in the spadix. Species 1. 

 (Greek lusis, loose, and chiton, a tunic or covering, referring to the spathe.) 



1. L. kamtschatcensis Schott; SKUNK CABBAGE. Coarse herb; leaves yel- 

 low, oblong to elliptic, 1 to l 1 /^ feet long and % to % feet wide ; peduncle stout, 

 shorter than the leaves ; flowering spadix about 1 inch long. 



Swamps along the coast : Santa Cruz Mts. to Humboldt Co. ; north to Alaska 

 and Siberia. 



Loes. Felton, M. L. Hutchinson; Ben Lomond, Gco. J. Stre.ator; Russian River (Fl. W. 

 Mid. Cal. ed. 2, 87); Ft. Bragg (Bot. Gal. 2:187); Eureka, Jepson; Little Van Duzen bridge, 

 ace. Tracy. Juneau, Alas., Jepson 479. 



Refs. LYSICHITON KAMTSCHATCENSIS Schott, Prod. Aroid. 421 (1860). Dracontium 

 Jcamtschatcense L. Sp. PI. 2:968 (1753), type loc. Siberia. 



LEMNACEAE. DUCKWEED FAMILY. 



Minute floating or submerged aquatic perennials, without leaves. Plant body 

 consisting of a leaf-like stem or "frond" which is densely green, disk-shaped, 

 elongated or irregular. Basal margin of the frond with 1 or 2 clefts or repro- 

 ductive pouches. Vegetative reproduction active, the daughter fronds arising 

 from the reproductive pouches and attached to the parent frond by slender stalks 

 (or stipes). Inflorescence, when present, consisting of a simple cluster of 2 

 staminate flowers and 1 pistillate flower, contained in the reproductive pouch, 

 subtended by a sac-like spathe, and imitating a single flower. Staminate flower 

 consisting of a single stamen and the pistillate flower of a single ovary with 1 to 

 7 ovules. Perianth none. Flowers and fruit scarce, in one genus unknown. The 

 daughter fronds soon separate or remain connected for some time ; they may at 

 certain seasons sink to the bottom of the pond or ditch and undergo a resting 

 period. Genera 4, species about 25, temperate and tropical zones. 



Bibliog. Hegelmaier, Friedr., Systematische Uebersicht der Lemnaeeen (Engl. Bot. J'ahrb. 

 21:268-305, 1895). Thompson, C. H., Revision of Am. Lemnaceae (Rep. Mo. Bot. Gard. 

 9:21-42, pis. 1-4, 1897). McAtee, W. L., Duckweeds [as wild duck foods] (U. S. D. A. 

 Bull. 205:3-5, 1915). 

 Fronds with roots; vegetative pouches 2, posteriorly placed. 



Frond 5 to 15-nerved, with several roots _ 1. SPIRODELA. 



Frond 1 to 5-nerved, with a single root 2. LEMNA. 



Fronds without roots, thin, strap-shaped; vegetative pouches 1 3. WOLFFIELLA. 



1. SPIRODELA Schleiden. 



Fronds with many fascicled roots. Roots with one vascular bundle. Repro- 

 ductive pouches 2, with cleft-like openings in either margin of the basal portion 

 of the frond. Inflorescence consisting of a cluster of 1 pistillate and 2 staminate 

 flowers borne in the reproductive pouches and subtended by a sac-like spathe. 

 Fruit round-lenticular, with winged margins. Species about 6, all continents. 

 (Greek speira, a cord, and delos, evident.) 



1. S. polyrhiza Schleiden. Fronds solitary or in colonies of 2 to 5, roundish 

 obovate, 5 to 15-nerved, iy 2 to 4 lines long, usually sterile. 



Southern California. Cosmopolitan. 



Locs. San Bernardino (Engl., Bot. Jahrb. 21:284); Pitt River (e. of Hat Creek), Br< u < r 

 2190. 



