Lewis . — The Life History of Griffithsia Bornetiana . 68 1 
calation of new phases. In other words, in the Uredineae the diploid genera- 
tion has become prolonged throughout the greater portion of the life-history. 
In the red algae, it seems likely that a similar postponement of 
reduction has taken place. In the Nemalionales, which is considered the 
most primitive group of the Rhodophyceae, the point of reduction is 
removed from the point of nuclear fusion only by the few cell-generations in 
the cystocarp (Wolfe on Nemalion , 90 ). In the higher forms, such as the 
Rhodomelaceae (Yamanouchi on Polysiphonia y 93 ), and the Ceramiaceae 
( Griffithsia ), nuclear reduction is separated from nuclear fusion, not only by 
the cell-generations of the cystocarp, but also by all the divisions of the 
vegetative cells of the tetrasporic plant. That is, the diploid phase has 
come to occupy the greater portion of the life-history. 
The biological meaning of this apparently general tendency in the 
evolution of plant structures is hinted at by the experiments of Gerassimow 
( 32 ). After studying the growth of vegetative cells of Spirogyra in which 
nuclei had been induced to fuse, Gerassimow came to the conclusion that 
the growth of a cell which has an unusual amount of nuclear material is 
more vigorous than that of a cell with the usual nuclear content. The 
cell-wall, the chromatophores, and apparently the protoplasm, grow more 
vigorously. Such cells divide only after they have reached a size noticeably 
larger than normal. (See Bot. Gaz., xxxv, 1903, pp. 224-5.) 
If, then, the presence of nuclei with the double chromatin content 
imparts greater vigour to the cell, we should expect to find some evidence 
of this greater vigour not only in the size, but in the rate of growth of the 
tetrasporic plants of Griffithsia. A comparison of sexual plants with 
tetrasporic plants does not reveal any constant difference in the size of the 
resting nuclei or in the size of the cells of the two kinds of individuals. How- 
ever, a comparison of those cells of the diploid individual which produce 
sori of tetraspores with the occasional cells of the haploid plant, which 
form similar structures, shows a difference in size, the cells with the diploid 
nuclei being larger (p. 67 2). 
More important from this standpoint is the fact that not only in 
Griffithsia , but in red algae generally where tetrasporic and sexual plants 
occur side by side, the tetrasporic plants are, as a rule, more abundant 
(p. 640). In Griffithsia Bornetiana the number of tetraspores produced 
is certainly much greater than the number of carpospores, and we should 
expect, therefore, if the two kinds of spores were equally vigorous, that the 
number of sexual plants would greatly exceed the number of tetrasporic 
plants ; whereas the reverse is the case. It seems possible that the carpo- 
spores have a greater capacity for development than the tetraspores. 
Cultural experiments along this line are much to be desired. 
If the view is correct that a postponement of reduction has occurred 
in some Rhodophyceae, it is evident that besides the alternation of the 
