70 LEMNACEAE. 



14. C. siccata Dewey. Rootstock creeping, clothed with short 

 lanceolate scales; stems slender, sharply angled, 15-60 cm, high, 

 scabrous abov^e; leaves rather rigid, 1-4 mm. wide, shorter than 

 the stems, scabrous on the margins above; bracts scale-like, the 

 lowest cuspidate, usually shorter than its spikelet; spikes oblong, 

 2-5 cm. long, 4-8 mm. broad, ferruginous; spikelets 4-12, alternate, 

 simple, ovoid, 4-16 mm. long, 2-8 mm. broad, crowded or distinct 

 below, the terminal pistillate at least at base, the intermediate 

 staminate or all variously mingled; scales ovate-lanceolate, acute, 

 ferruginous, with broad hyaline margins; perigynium oval or ovate, 

 tapering to a long, sharply bidentate beak, fissured on the outer side, 

 unequally serrate on the margins, plano-convex, nerved, about 

 equaling the scale; nutlet oblong, dark chestnut. 



Common on borders of marshes throughout our ranges. Cienega; 

 Playe del Rey; Santa Ana; San Bernardino. 



Family 11. LEMNACEAE. Duckweed Family. 



Minute perennial floating plants, without leaves or 

 with only very rudimentary ones. The plant body con- 

 sisting of a disk-like thallus, with usually 1 or more 

 rootlets from the middle below. Florets imbedded in 

 the frond, without perianth, naked or bracteate, with 1-2 

 stamens and a sessile 1 -celled, 1-several-ovuled ovary. 

 Style simple with funnelform stigma. Fruit a utricle; 

 embryo straight. 



Roots I or more. 



Roots more than 1, fascicled. 1. Spirodela. 



Root solitary. 2. Lemna. 



Roots none. 3. Wolffiella. 



1. SPIRODELA Schleiden. 



Stipe attached (peltately) to the frond back of and 

 under the basal margin. Reproductive pouches 2, tri- 

 angular, opening as clefts in either margin of the basal 

 portion of the frond. Roots more than 1, fascicled. 

 Spadix of 1 pistillate and 2 staminate flowers from the 

 reproductive pouches; spa the sac-like; filaments curv- 

 ing upward from the margin of the frond; anthers 

 2-celled, longitudinally dehiscent. Fruit rounded len- 

 ticular, with wing margins. 



1. S. polyrhiza (L.) Schl. Fronds solitary or united in colonies 

 of 2-5, roundish obovate, flat on both sides, sessile or nearly so; 

 5-15-nerved, 3-6 mm. long, 2.5-4.5 mm. wide; roots 4-16; rootcap 



