i66 A TEXTBOOK OF THEORETICAL BOTANY 



InPolysiphonia violacea, another species which has been fully investigated, 

 the development of the procarp branch after fertilization is somewhat more 

 complex (Fig. 156). Instead of a single auxiliary cell, a number are formed, 

 and these are produced, not from the basal cell of the procarp branch but 

 from the pericentral cell. This cell cuts off two cells, one of which divides 

 once again ; the other produces a cluster of five cells, which lie beside the 



PERICENTRAL 

 CELL 



CARPOGONIUM 



PERICENTRAL CELL 



TRICHOGYNE . 



TRICHOGYNE 



CARPOGONIUM 



AXIAL 

 SIPHON 



CARPOGONIUM 



'a.B 



Fig. 156. — PolysipJwnia violocea. A to E, Stages in the development of the 

 procarp branch. B, Transverse section. F, Formation of auxiliary 

 cells. {After Yamanouc/i!.) 



carpogonial branch. The end cell of the group (0.2) lies between the carpo- 

 gonium and the pericentral cell. 



I'he fertilized nucleus in the carpogonium divides, and meanwhile cyto- 

 plasm from the cells of the procarp branch passes into the carpogonium, 

 presumably as nourishment. A wide protoplasmic connection now develops 

 between the carpogonium and the auxiliary cell (a. 3) which in turn becomes 

 united wath the pericentral cell. Through the channel thus formed the two 

 diploid nuclei from the carpogonium pass into the pericentral cell. The 

 carpogonium and the cells of the procarp branch now disorganize. The 

 avivil.irs^ cells next draw closer together, and wide protoplasmic connections 



