528 



THE AMEBIC AX NATURALIST [Vol. XLIV 



A detailed study by Lewis 10 of the life history of Grif- 

 fithsia is in agreement with the results of Yamanouchi 

 on the essential facts of an alternation of sexual and 

 tetrasporie plants and the behavior of the chromosomes 

 throughout the various phases of the similar life his- 

 tories. The sexual plants have seven chromosomes, the 

 haploid number. The oystocarp presents nuclei with 

 fourteen chromosomes and is clearly a sporophytie phase 

 which, as in Poly.siphoiria, develops with the cooperation 

 of the cytoplasm in certain cells of the gametophyte; the 

 carpospores have fourteen chromosomes. The tetra- 

 sporie plants are characterized by fourteen chromosomes, 

 the diploid number, and may be assumed to arise from 

 the carpospores. The first mitosis in the tetraspore 

 mother-cell is a reduction division preceded by the char- 

 acteristic stage of synapsis from which the chromosomes 

 emerge in seven pairs. Seven chromosomes, therefore, 

 pass to the tetraspores from which the sexual plants 

 may be expected to develop. 



It is known that in a number of species of red alga 1 

 structures resembling tetraspores are occasionally found 

 on sexual plants and that procarps are sometimes pres- 

 ent on tetrasporie individuals. Such conditions, first ob- 



Lotsv for Clmh.chuVu, knlifonuis. Yamanouchi for Poly- 

 siphonia violacea, Lewis for Griffithsia Bornetiana, and 

 by the writer for Spermothamnion Turneri, Callitham- 

 nion Bailey i and Ceramium pedicillatum. Furthermore, 

 certain of the red algae, as Rhodymenia palmata on the 

 New England coast, present tetrasporie plants in great 



ous difficulties for the theory of alternation of genera- 

 tions in the Rhodophyeea? so strongly supported by the 

 work of Yamanouchi and Lewis. 



These authors had only limited material of what seemed 



