HEP A TIC.-E 



163 



each archegone being, in addition, usually surrounded by a distinct mem- 

 branous envelope, the perianth ox perigyne. 



In the formation of the sporogone, the fertilised oosphere first divides 

 by a wall at right angles to the axis of the archegone. Only the upper 

 of the two cells thus formed — that is, the one that faces the neck of the 

 archegone — undergoes further divisions ; it becomes the apical cell of 

 the sporogone, and sometimes again divides transversely once or twice 

 before a longitudinal wall makes its appearance in it ; the two cells thus 

 formed finally divide into four apical cells arranged as octants of a hemi- 

 sphere. The basal portion of the growing archegone swells out and 

 penetrates down into the tissue of the stem, forming the valine. 



Fig. 141. — Sexual organs of R adicla 

 complatiata. ar^ archegone ; an^ an- 

 therid ; b, leaf, (After HofmeLter.) 



Fig. 142. — Jungerviann'a bicuspidata L. Longi- 

 tudinal section of immature sporogone, sg ; ar, 

 calypter ; ar" , unfertilised archegones ; /, base of 

 perigyne ; st, stem ; b, leaf. (After Hofmeister.) 



After frequent divisions have taken place, the wall of the spore-capsule 

 becomes differentiated from the inner tissue, out of which are developed 

 the spores and elaters. There is no columel. By rapid extension of 

 the hitherto short pedicel, the calypter is ruptured at the apex, and the 

 globular sporogone, containing the already ripe spores, becomes elevated. 

 The inner of the two layers of which the wall of the sporogone is com- 

 posed has become absorbed before the ripening of the spores ; the single 

 layer of cells which still remains is ruptured at the apex, and splits into 

 four (rarely more) longitudinal valves, which separate suddenly in the 

 form of a star, carrying with them at the same time the elaters, and thus 

 bringing about the dispersion of the spores. The mature elaters are 



M 2 



