CL. II.] DIANDRIA MONOGYNIA. 57 



9. LE'MNA. DUCKWEED. 



Calyx of one leaf, membranous. Corolla none. Stamens 

 thread-shaped, lateral, unequal, longer than the calyx. Anthers 

 of two globes. Germen superior, egg-shaped. Style shorter than 

 the stamens. Capsule one-celled, globose, containing one seed. 

 Name from lemma, a scale. 14. 



1. L. triscul'ca. Ivy-leaved Duckweed. Fronds stalked, between ellip- 

 tical and lance-shaped, thin, serrated towards the point ; roots solitary. 



Fronds about half an inch long, reticulate, pellucid at the margin : 



leaf-stalks issuing from the sides of another leaf, from a fissure there : 

 capsule egg-shaped, pointed, sitting on the upper surface of the frond. 

 Annual: flowers from June to September: occurs floating in ditches, 

 pools, and lakes : common. All the species of this genus are said to be 

 eaten by ducks and other herbivorous aquatic birds. Eng. Bot. vol. xiii. 

 pi. 926. Eng. Fl. vol. i. p. 32. 47. 



2. L. minor. Lesser Duckweed. Fronds inversely egg-shaped, ser- 

 rated, compressed, the lower stalked ; roots solitary. Fronds two or 



three lines long, rather thick and firm : flowers from June to September. 

 Annual : occurs floating in dense masses, in ditches, pools, and lakes : 

 very common. Eng. Bot. vol. xvi. pi. 1095. Eng. Fl. vol. i. p. 32. 48. 



3. L. gib'ba. Gibbous Duckweed. Fronds inversely egg-shaped, 



hemispherical beneath ; roots solitary. Fronds about a line long, 



green and plane above, bulging and purple beneath. Annual : flowers 

 from June to September : occurs floating in ditches, pools, and lakes : 

 rare in Scotland ; in England and Ireland not unfrequent. Eng. Bot. vol. 

 xviii. pi. 1233. Eng. FL vol. i. p. 32. 49. 



4. L. polyrhiza. Greater Duckweed. Fronds broadly egg-shaped, a 



little convex beneath ; roots numerous. Fronds half an inch long, 



firm, green above, purple below. Annual : flowers unknown in Great 

 Britain, occurs floating in stagnant water : rare. Eng. Bot. pi. 2458. 

 Eng. Fl. vol. i. p. 33. 50. 



10. CLA'DIUM. TWIG-RUSH. 



Calyx a one-valved chaff-scale, concave, one-flowered. Co- 

 rolla none. Stamen thread-shaped, longer than the husk. An- 

 ther linear, erect. Germen superior, egg-shaped, without bristles 

 at the base. Style thread-shaped. Drupe egg-shaped, one-celled ; 

 nut hard, egg-shaped, acute. Name from klados, a branch. 15. 



1. C. Mariscus. Prickly Twig-rush. Panicle repeatedly divided ; 

 stem round, smooth, leafy ; leaves prickly at the edge and along the 



keel. Root long, and creeping : stem four or five feet high, erect, 



angular at the top : leaves keeled, ending in a sharp point, with prickly 

 serratures : panicle erect, with numerous compound, furrowed branches. 

 Perennial : flowers in July and August : grows in marshes and bogs in 

 several parts of England : rare. Cunnemara bogs, Ireland. Very rare 

 in Scotland ; Sutherlandshire ; formerly found in the moss of Restenat, 

 near Forfar, but now extinct there. Eng. Bot. pi. 950. Eng-. Fl. vol. i. 

 p. 36. Brit. Fl. p. 13. 51. 



