78 Lemnaceae 



2. LEMNA L. DUCKWEED. 



Stipe attached to the basal margin of the frond. Re^ 

 productive pouches 2, triangular, opening as clefts in 

 either margin of the basal portion of the frond. Root 

 solitary. Spadix of 1 pistillate and 2 staminate flowers ; 

 spathe various ; filaments curving upward from the mar- 

 gin of the frond. Anthers 2-celled, transversely dehis- 

 cent. 



1. It. gibba L. Fronds from solitary to 4 in a colony, com- 

 monly 2, orbicular to obovate, 2-5 mm. long, 2-4 mm. wide, more 

 or less unsymmetrical, thick, convex and slightly keeled above, 

 usually more or less gibbous beneath, usually 3-5-nerved; fruit 

 winged with rounded lobes on either side of the stigma ; seeds 1-7. 



Common in slow-running streams and ponds. 



2. L. minor L. Fronds solitary or with 2 or more in a colony, 

 round to elliptic-obovate, 2-4 mm. long, 1.5-3 mm. wide, sym- 

 metrical, thickish, convex on both sides, upper surface sometimes 

 keeled and with a row of papulae along the midnerve, obscurely 

 3-nerved; fruit not winged ; seeds solitary. 



Apparently less common than the last. 



3. L. cyclostasa (Ell.) Chev. Fronds commonly in colonies 

 of 2-8, oblong to obovate-oblong, usually somewhat falcate, 2.3-4.5 

 mm. long, 0.7-1.5 mm. wide, usually strongly unsymmetrical; 

 fruit elongated-ovate, slightly unsymmetrical ; seed oblong-ovoid. 

 (L. Valdiviana Phil.) 



Common throughout our range. 



4. L. minima Phil. Fronds commonly in colonies of 2, ob- 

 long to elliptic, 1.5-3.9 mm. long, 0.9-2.7 mm. wide, slightly to 

 prominently convex above, with a row of papulae along the mid- 

 nerve, convex below, commonly nerveless; pistil short, clavate; 

 seed oblong, pointed. 



Near San Bernardino, Parish; Bear Valley, San Bernardino Mountains; 

 Lakeside, San Diego County. 



5. L. trisulca L. Fronds floating and submerged, oblong to 

 oblong-lanceolate, with a long stipe attached to the basal margin ; 

 often somewhat falcate, 5-10 mm. long, 2-3 mm. wide; terminal 

 margins serrulate and fluted, acute at apex. 



Bear Valley, San Bernardino Mountains. 



