Lemnaceae 7< 



midnerve, margin hyaline; perigynium oval, abruptly tapering 

 to a sharply bidentate beak, serrate above on the sharp incurved 

 margins, shorter than the scale. 



Frequent on borders of the coast ma rshes . 



Family 8. 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 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; spathe sac-like; filaments curv- 

 ing upward from the margin of the frond ; anthers 

 2-celled, longitudinally dehiscent. Fruit rounded lenticu- 

 lar, 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 

 large, sharp pointed ; spathe a complete sac, opening at the upper 

 end: pistil flask-shaped; fruit somewhat winged; seed slightly 

 compressed, smooth. 



Near San Bernardino, Pariah. This, as well as all the other members of 

 the family occurring with us, is rarely fertile. 



