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 
Fic. 41. 
Conjugation of Rhopaledia, after Klebahn. %, nucleus; £4, small nucleus ; ¢4, large 
nucleus ; #7, pyrenoid ; g, mucilage. (From Oltmanns.) aia : 
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 
