130 



PLANT-LIFE 



Riella helicophylla is aquatic; it is thus described by 

 Montagne: " Figure to yourself an axis consisting of a 

 nerve round which is wound in a most regular and 

 elegant spiral a membranous wing of the width of 

 5 millimetres, of the most beautiful green, and of ex- 

 treme delicacy, in such manner as to form with it a kind 

 of gimlet or helix in inverted cones." Species of Riella 

 have been found in regions adjacent to the Mediter- 

 ranean, the Canary Islands, and the United States. 



Fig. 41. — General View of a Single 

 Plant of the Liverwort (Pellia 

 epiphylla). 



oo, Lobed thallus, the gametophyte 

 generation; sp, the fructifications, 

 the sporophyte generation. About 

 hah natural size. 



r./i. 



Fig. 42. — Pellia epiphylla, 

 Portion of Thallus seen 

 from Above. 



an, Antheridia; r.h., root-hairs. 



LcpJwcolea bidentata, the Two-Toothed Liverwort, is also 

 very common in Britain in shady situations; I have 

 found it growing on wet rocks, on earth, and among 

 Mosses. It is a good example of the more delicate foliose 

 Hepatics; its pale green leaves each bear two strongly 

 outlined teeth at the apical margin. 



The Tubercled Liverwort, Frullania dilatata, another 

 of the leafy forms, grows on the bark of trees, and may 



