30 LEMNA. [CLASS 11. ORDER i. 



2. L. polyrrhi'za, (Fig. 41.) greater Duckweed. Fronds ovato-rotun- 

 date compressed, roots numerous in clusters. 



English Botany, t. 2458. English Flora, vol. i. p. 33. Lindley, 

 Synopsis, p. 252. Hooker, British Flora, vol. i. p. 13. 



The largest of the genus, and well distinguished by its clustered 

 roots growing from the point of union where the fronds unite. Fronds 

 about half an inch long, and nearly as broad, striated above with a 

 dark purple margin, somewhat convex beneath, of a purple colour. 

 Flowers not known in Britain. " Wiggers records a young German, 

 named Graver, as having found the flowers, situated where the fronds 

 overlay each other, in July and August. The seed proved larger and 

 flatter than in L. gibba" Smith. 



Habitat. Ditches and pools, not common ; Nottingham meadows. 



Annual. 



3. L. gib'ba, (Fig. 42.) gibbous Duckweed. Fronds broadly obovate, 

 slightly convex above, hemispherical, and pale beneath, roots soli- 

 tary. 



English Botany, t. 1233. English Flora, vol. i. p. 32. Lindley, 

 Synopsis, p. 252. Hooker, British Flora, vol. i. p. 13. 



Larger than L. minor. Fronds green above, in a young state flat, 

 pale beneath, and gradually swelling until almost hemispherical, first 

 commencing to swell at the base of the root, until at length the en- 

 larged pellucid cellules burst; the fronds then turn yellow, and shortly 

 decay. Roots solitary. Flowers from the margin of the frond, peri- 

 anth scarcely visible. This species somewhat resembles L. minor, but 

 is readily distinguished by its large cellular and gibbous, or hemisphe- 

 rical under surface. " Capsule four-seeded. Seed furrowed, not 

 transversely placed, but with the hilum towards the top of the cap- 

 sule." Wilson in Br. Fl. 



Habitat. In stagnant waters, not so common as the following spe- 

 cies. 



Annual ; flowering from June to September. 



4. L. mi' nor, (Fig. 43.) lesser Duckweed. Fronds nearly ovate com- 

 pressed, slightly convex beneath, roots solitary. 



English Botany, t. 1095. English Flora, vol. i. p. 32. Lindley, 

 Synopsis, p. 252. Hooker, British Flora, vol. i. p. 13. 



Fronds from one to two lines long, irregular, plane or slightly con- 

 vex above as well as beneath, where it is of a pale colour, somewhat 

 fleshy, and of a more compact texture than L. gibba. Flowers similar 

 to the last. " The capsule is single-seeded ; seed transverse, with its 

 hilum ' directed towards the narrow end of the frond.' " Hooker. 

 This is the most common of all the species, increasing with great rapi- 

 dity by gemma; or buds, frequently covering the surface of extensive 

 pools of stagnant water, and often considered a troublesome intruder 

 in fish-ponds. Ducks and other water-fowl feed upon it, hence 



