665 



CHAPTER X 



MICROSCOPIC STRUCTURE OF THE HIGHER CRYPTOGAMS 



Hepaticse. Quitting now the algal and fungoid types, and 

 entering the series of terrestrial cryptogams, we have first to notic 

 the little group of H?j>atica\ or liverworts. This group presents 

 numerous "objects of great interest to the microscopist ; and no 

 species is richer in these than the very common Marchantia poly- 

 iiiorpliH. which may often be found growing between the paving- 

 stones of damp courtyards, but 

 which particularly luxuriates in 

 the neighbourhood of springs or 

 waterfalls, where its lobed fronds 

 are found covering extensive sur- 

 faces of moist rock or soil, adher- 

 ing by the radical filaments (rhi- 

 zoids) which arise from their lower 

 surface. At the period of fructi- 

 fication these fronds send up 

 stalks, which carry at their sum- 

 mits either round shield-like discs, 

 or radiating bodies that bear some 

 resemblance to a wheel without 

 its tire (fig. 503). The former 

 carry the male organs or a>i- 

 tkerids ; while the latter in the first instance bear the female 

 organs or archegoiies, which afterwards give place to the ni>oru ij< *. 

 or spore-cases. 1 



The green surface of the frond of Marchantia is seen, under a low 

 magnifying power, to be divided into minute diamond-shaped spaces 

 (fig. 504, A, , a), bounded by raised bands (c, c) ; every one of these 

 spaces has in its centre a curious brownish-coloured body (b, />), with 

 nil opening in its middle, which allows a few small green cells to be 

 seen through it. When a thin vertical section is made of the frond 

 (B), it is seen that each of the lozenge-shaped divisions of its surface 

 corresponds with an air-chamber in its interior, which is bounded 

 below by a floor (a, f/) of closely set cells, from whose under surface 

 the rhizoids arise ; at the sides by walls (c, c) of similar solid 



FIG. 503. Froud of Marchantia 



niorplia, with gemmiparous concep- 

 tacles, and lobed receptacles bearing 

 archegones. 



1 In some species the same shields bear both sets of organs ; and in Ma reliant id 

 androgyna we find the upper surface of one half of the shield developing antherids, 

 whilst the under surface of the other half bears archegoiies. 



