f 

 Lemna. LEMNACEJ3. 189 



late flowers without bracts : pollen-grains in fours. Bohrbach, Verb. Ver. Brandenb. 

 xi. 38, and Amer. Journ. Sci. 3 ser. ii. 375 ; Reichenb. Icon. Fl. Germ. ix. t. 323. 



Common in marshes from the Sacramento northward, and found throughout most of North 

 America, and in the Old World. 



2. T. angUStifolia, Linn. Leaves usually narrower, somewhat convex on the 

 back : pistillate and staminate inflorescence usually separated by a short interval, 

 the spike becoming 5 or 6 lines in diameter : pollen-grains simple : pistillate flowers 

 with a linear stigma, and a hair-like bract slightly dilated at the summit. Rohrbach, 

 1. c.; Reichenb. 1. c., t. 321. 



Collected at Soda Lake in Southeastern California (Dr. Cooper) and at Los Angeles (Rev. J. C. 

 Nevin) ; also in the Atlantic States, but less common than the last, and in the Old World. 



* 



ORDER CXIII. LEMNACE-SE. 



Very small floating herbaceous perennial stemless plants, consisting of flattened 

 disk-like fronds, with usually one or more rootlets from the middle below ; florets 

 imbedded in the frond, without perianth, naked or bracteate, with 1 or 2 stamens 

 and a sessile 1-celled 1 - several-ovuled ovary (each organ by some botanists con- 

 sidered a distinct flower) ; style simple, with funnelform stigma ; ovules at the base 

 of the cell; fruit a utricle; seeds comparatively large, albuminous with straight 

 axile embryo, the testa operculate at the apex. Hegelmaier, Die Lemnaceen. . 



Comprising only three genera and perhaps 20 species, found on still waters in temperate and 

 tropical regions. The smallest of all flowering plants, rarely found in flower or fruit, propagating 

 by buds from lateral or basal slits, the young fronds at length separating. In autumn the buds 

 or bulblets sink into the mud, to rise again in the spring. Only one genus is positively known as 

 California!!, but both the others will probably be found. The third genus, Wolffia, is distin- 

 guished by its minute size, the thick rootless fronds being only to of a line broad. The 

 flowers are naked, and have a single stamen with a 2-celled anther, and a 1-ovuled ovary. 



1. Lemna. Frond 1 -5-nerved, with a single rootlet. 



2. Spirodela. Frond 7- 11-uerved, with several rootlets. 



1. LEMNA, Linn. DUCKWEED. DUCK'S-MEAT. 



Flowers marginal, bracteate, diandrous. Filaments slender ; anthers didymous, 

 each cell bilocellate by a transverse partition, dehiscing transversely. Seeds 1 to 6, 

 mostly ribbed. Frond 1 - 5-nerved, containing numerous acicular raphides, pro- 

 liferous from a lateral slit (usually on each side) near the base, with a single rootlet, 

 which is destitute of vascular tissue. 



* Ovule solitary, orthotropous or nearly so : frond 1 3-nerved, thin. LEMNA 



proper. 



t Fronds oblong, stalked at base, remaining connected. 



1. L. trisulca, Linn. Fronds thin, oblong or oblong-lanceolate, 6 to 9 lines 

 long, attenuate at base into a slender stalk, very obscurely 3-nerved, often without 

 rootlets, usually several series of offshoots remaining connected : bract sac-like : 

 seeds ovate, amphitropous, with small round operculum. Hegelm. 1. c. 134, t. 5, 6; 

 Reichenb. Icon. Fl. Germ. vii. 9, t. 15. 



Near San Francisco and on San Gabriel Creek (Bigelow) ; Plumas County (Lemmori) ; Oregon, 

 and eastward through most of North America, as also through Europe, Asia and Australia. 



i -i Fronds oblong to elliptical or round-ovate, sessile, soon separating. 



2. L. Valdiviana, Philippi. Fronds elliptic-oblong, small (a line long or 

 usually less, rarely more), rather thick, obscurely 1-nerved : bract broad - re ni form : 



