oD*m.J LEMNA. 29 



is a favourite habitat of many species of crustaceous Lichens ; and on 

 it alone have we found the beautiful genus of insects, C/u/ocornw 

 the species C. renipustulatu* is very plentiful in plantations in Notting- 

 hamshire aud Yorkshire. 



GENUS IX. LEM'NA. Duckwttd. 

 Nat. Ord. PIS'TIACE^:. 



GfiN. CHAR. Perianth single, membranous, inflated. Fruit a thin 

 transparent membranous utricule, single-seeded. Small floating 

 smooth lenticular plants, with lateral proliferous fronds. Capable 

 of reproduction by seed, but most abundantly by gemmee or buds; 

 each frond having one or more pendulous thread-like roots. Name 

 said to be derived from ^WML, Lemma, the meaning of which, in 

 reference to the plants in question, is very obscure ; some authors 

 suppose it to be from XETTJ?, Lepis, in allusion to the squamous or 

 scale-like appearance of the fronds. Jussieu, in consideration of 

 the convex or lenticular-shaped fronds of this genus, has given 

 them the more descriptive, and therefore better, name of Lenticula, 

 for Lemna. Aware, however, of the inconvenience, and even dis- 

 gust, which is felt at the needless change often recommended in 

 opposition to the advantages which would arise from a less muta- 

 ble nomenclature, we prefer retaining the latter. 



1. L. tritul'ca, (.Fig. 40.) Ivy-leaved Duckweed. Fronds stalked, 

 thin, elliptico-lanceolate, serrated at the extremity, root slender, 

 and solitary. 



English Botany, t. 926. English Flora, vol. i. p. 32. Lindley, Sy- 

 nopsis, p. 251. Hooker, British Flora, vol. i. p. 13. 



Fronds from half to three quarters of an inch long, pale green, pel- 

 lucid at the margin, frequently waved or serrated ; young plants are 

 rapidly produced from lateral clefts in the broadest part of the fronds, 

 and grow mostly at right angles with the parent plant, and of the same 

 form : these also become proliferous while attached to the parent frond, 

 thus becoming repeatedly compound, each frond emitting from the 

 centre of its under side a solitary pendulous root, curiously tipped at 

 the extremity, with a small conical sheath. Flower very small, arising 

 in this and the rest of the genus from lateral clefts in the fronds. 

 Stamens two, unequal. Anther divided, globular. Stigma obtuse, 

 scarcely protruding from the perianth. 



Habitat. Clear stagnant waters : not very common in England, but 

 more so than in Scotland. Plentiful in the drains about Lincoln, and 

 Newark, Nottinghamshire. 



Annual ; flowering in June and July. 



