CL. II.] DIANDJUA 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 el- 

 liptical 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 : oc- 

 curs 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, ihe lower stalked ; roots solitary. Fronds two 



or three lines long, rather thick and firm : flowers from June to Sep- 

 tember. 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 unfre- 

 quent. 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, fur- 

 rowed branches. Perennial : flowers in July and August : grows 

 in marshes and bogs in several parts of England : rare. Cunne- 

 mara bogs, Ireland. Very rare in Scotland ; Sutherlandshire ; for- 

 merly found in the moss of Resteiiat, near Forfar, but now extinct 

 there. Eng. Bot. pi. 950. Eng. Fl. vol. i. p. 36. Brit. Fl. p. 1 3. 51 . 



