456 



BOTANY OF THE LIVING PLANT 



The origin of a somatic development, or formation of a plant-body, 

 may be at either of two points in the life cycle : often at both 

 points. This has already been foreshadowed in such Thallophytes 



Fig. 35-^. 

 Catharinea (Atrichitm) undulata. The leafy gametophyte, or Moss Plant, bearing 

 capsules, or sporogonia, which are the dependent sporophyte generation. (After 

 Schimper.) 



as Dictyota (p. 384), and Polysiphonia (p. 387), both of which show 

 two alternating " generations." The limits between these are on the 

 one hand the zygote, in which by syngamy the chromosomes 

 are doubled in number : on the other the tetrad-division, in which 



