Ricda.] HEPATIC^. 213 



and which grows in more shady and moist situations, has the 

 frond generally longer, broader, much thinner, nearly plane, 

 with segments more numerous and very obtuse, the colour by 

 no means glaucous, rather, perhaps, inclining to yellowish 

 green. Frond growing in orbicular tufts radiating from the 

 centre. The fronds, in all, when seen in a fresh state, from 

 the delicate and pellucid nature of the cellules, which are par- 

 ticularly convex, have a remarkably crystalline appearance, 

 not unlike that of Mesembryanthemum crystallinum ; which has 

 determined us to prefer, of the equally ancient names, that of 

 crystallina. 

 2. R. ?fluitans ; aquatic, floating, frond thin repeatedly forked, with 



linear obtuse segments generally notched at the extremity. 

 Riccia fluitans. Linn. Sp. PL p. 1606. Engl Bot. 't. 251. 



Weber, Prodr. Hepat. p. 117. Schwaegr. Prodr. Hepat. p. 38 Dill 



Muse. t. 74. /. 17. 



HAB. Stagnant waters, floating upon the surface. Not 

 found in Scotland. 



Fronds varying from half an inch to two inches in length, 

 yellow green, repeatedly divided in a dichotomous .manner, the 

 segments linear, not more than half a line in breadth, slightly 

 thickened in the centre, as if furnished with an obscure midrib, 

 grooved in the upper surface, when dry, thin, semipellucid ; re- 

 ticulation indistinct ; the extremities obtuse, occasionally spha- 

 celated, and opaque, having the appearance of spots, which 

 some have considered an incipient fructification, but we can 

 find no peculiar organization about them, nor has any thing 

 like real fruit been discovered. The plant commonly grows 

 upon the surface of the water in ponds and ditches, where it 

 assumes its largest size, and is quite destitute of fibrous 

 radicles ; not unfrequently, however, perhaps left by the sub- 

 siding of the water, it is found upon the soil ; it is then smaller, 

 with the segments shorter, throwing out numerous fibrous 

 roots from its whole under surface, with which it adheres 

 firmly to the place of growth, and has then very much the 

 appearance of some of the narrower and thinner varieties of 

 It. crystallina. Still we think the nature and reticulation of the 

 frond are different ; but farther observations are required to 



decide this point. Ehrhart, in his Beitrage, v. III. p. 81., 



O 3 



