72 ALTERNATION IN THE THALLOPHYTES 



but in both cases half of the nuclei produced are discarded : this would 

 seem to point to some special importance attaching to the division into 



FIG. 41. 



Conjugation of Rhopalodia, after Klebahn. k, nucleus ; kk, small nucleus ; gk, large 

 nucleus ; fy, pyrenoid ; g, mucilage. (From Oltmanns.) 



four, and by analogy with what is seen elsewhere it would appear probable 

 that the importance lies in a process of reduction accompanying it. What- 

 ever the actual cytological condition may be, at all events this is clear, 

 that, in these strangely similar plants, the tetrad-division of the nuclei 



