274 



STRUCTURE OF LEAFY HEPATICS 



Some of these cells of the capsule develop as spore mother cells, 

 while others, known as elaters, elongate greatly and serve to con- 

 duct the foods absorbed by the foot to the spore mother cells, and 

 finally they become spirally thickened (Fig. 

 194, C). During the germination and growth 

 of the gametospore, a delicate membrane (the 

 perianth) grows up about the archegonium 

 and doubtless assists the involucre in protect- 

 ing it against drying winds (Fig. 193, p). 

 When the spores are mature, the cells of the 

 stalk elongate, rupture the archegonium and 

 push the capsule beyond the curtains of the 

 perianth and involucre, so that it is exposed 

 to the air (Fig. 195). The capsule now rup- 

 tures, exposing the spores and elaters to the 

 air. The elaters, a word meaning lifters, are 

 very hygroscopic; they coil and uncoil with 

 the least change in the humidity of the air 

 and thus doubtless assist in the gradual ex- 

 posure of the spores to the air currents. The 

 spores germinate as in the lower liverworts. 

 Thus we see that the sporophyte, consisting of 

 Fig. 196. One a foot, stem and capsule, is more complex and 

 of simpler thai- larger than in Ricciocarpus. This is doubt- 

 Jungermani- j^^^ ^^^^ ^^ ^^le better nourishment which it 

 receives as a result of the development of a 

 more efficient absorbing organ, the foot. 



105. Order b. Jungermaniales or Leafy 

 Hepatics. — By far the larger number of 

 hepatics belong to this order. They are espe- 



a cup-like perianth cially abundant in moist tropical countries, 



which is surround- ^^^^^ ^^ ^^^^^ ^^^^^ ^j^^ ^^^^^ ^^^ Ig^^.^S 



ed at Its base with , • 1 1 r 



involucrate leaves, with a rich vegetation, and with us they are ot 



H. O. Hanson. common occurrence on dripping rocks and in 



deep woods on the moist bark of trees and de- 

 caying logs or damp earth. In the lower form the thallus is very 

 simple and delicate (Fig. 196). In other genera there are indica- 



loid 



ales, Pnllavicinia, 

 showing the rhi- 

 zoidal growth on 

 the under surface 

 of the thallus and 

 a mature sporo- 

 phyte arising from 



