316 



PART IV. CLASSIFICATION. 



that there is no continuity of tissue between the two generations ; 

 the sporophyte is simply inserted into the tissue of the gameto- 

 phyte. In the Hepaticse (except Anthoceros) the sporophyte is 

 short-lived, and is entirely dependent upon the gametophyte for its 

 nutrition. In Anthoceros, and in most of the Musci, the capsule 

 possesses more or less well-developed assimilatory tissue, and its 

 epidermis is provided with stomata, so that the sporophyte is 

 capable of using the carbon dioxide of the air as its carbonaceous 

 food, and is dependent upon the gametophyte only for its supply 

 of water and salts. In many of these forms the seta has a central 

 strand of rudimentary vascular tissue through which the water 

 and salts, absorbed from the gametophyte, can travel to the region 

 of the capsule where assimilation and transpiration are carried on. 



FIG. 197. Comparative morphology of the sperogonium in the Bryophyta : diagram- 

 matic transverse sections of the young capsule. A Sphserocarpus (typical Liverwort) ; B 

 Ceratodon (typical Moss) ; C Anthoceros (aberrant Liverwort). E Endothecium : 9-9 

 primary divisions (quadrant and octant walls) ; s (shaded) archesporium ; C columel'.a. 

 (A and C after Leitgeb ; B after Kienitz-Gerioff.) 



The tissue of the developing capsule becomes differentiated into 

 an external layer (or layers) of cells, termed the amphithecium, 

 which, in nearly all cases (except Anthocerotacese and Sphagnacese) 

 forms only the wall of the capsule ; and an internal solid mass of 

 cells, the cndothecium. The spores are developed from a mass or 

 a layer of cells termed the archesporium. In the Hepaticae the 

 archesporium (Fig. 197 .4) includes the whole of the endothecium 

 (except in Anthocerotacese, Fig. 197 (7), and the archesporial cells are 

 either all sporogenous (Ricciese) or, as is more frequently the case, 

 some of them are sterile and generally become spirally thickened 

 and elongated in form when they are termed elaters. In the Antho- 



