680 Lewis. —The Life History of Grijftthsia Borne liana. 
the sporogenous cells of the cystocarp as belonging to the sporophytic 
phase of an antithetic alternation of generations. The point of departure 
lies in the interpretation of the tetraspore-producing plant. Because of its 
general morphological identity with the gametophyte, Oltmanns regards 
this as a part of the gametophyte, which has become differentiated for the 
production of tetraspores. Because of the diploid condition of its nuclei, 
Yamanouchi regards the tetrasporic plant as a part of the sporophyte, 
whose resemblance to the gametophyte is stamped on it by ‘ similar 
environmental conditions a view in which Bower (12, p. 81 ) seems to concur. 
For the purposes of the present discussion, I shall assume from the 
cytological evidence what it will take cultural experiments to prove, namely, 
that in those red algae in which tetraspores and gametes are regularly 
formed on separate individuals there is an actual succession of sexual and 
tetrasporic plants, the reproductive bodies of one kind of plant always 
producing the other kind of plant. 
Yamanouchi’s suggestion (93) that the tetrasporic plant may have 
arisen phylogenetically by the postponement of the phenomena of reduction 
from the formation of carpospores to the production of asexual spores 
seems to be rendered probable by what we know of other groups of plants. 
In the simplest plants which have been investigated from this standpoint, 
the position of reduction in the life-history seems to be at the first divisions 
of the fusion nucleus, as is described in Coleochaete (Allen, 2), certain 
desmids (Klebahn, 47), and in Spirogyra (Karsten, 45). Beginning with 
the simple Bryophytes, the familiar Archegoniate series shows a progressive 
removal of the point of reduction from the point of fusion of the sexual 
nuclei. These and other examples seem to show that there is a general 
tendency throughout the plant kingdom to prolong the diploid condition of 
the nucleus through the greater part of the life-history (see Bower, 12, p. 77 ). 
Nowhere is this more plainly shown than in the Uredineae (Blackman, 
8 ; Blackman and Fraser, 9 ; Christman, 16, 17). This group is charac- 
terized by a succession of phases, or generations, which have been shown by 
Christman to be morphologically equivalent, though each ends in a distinct 
form of spore. Now nuclear association, which has been regarded as the 
equivalent of fertilization in this group, occurs, in all forms in which the 
aecidial stage is present, in those cells of the mycelium which give rise to 
the aecidium. The process of numerical reduction of the chromosomes, 
or, to speak more accurately, of the chromatin, occurs always in the last 
spore-form preceding the production of aecidia, in the teleutospore when 
present The diploid condition, extending from the aecidium to the 
teleutospore, is lengthened by the intercalation of new phases, which, in 
some cases, seem to have the power of continuing the diploid generation 
indefinitely. The haploid generation, from the teleutospore to the binu- 
cleate cells at the base of the aecidium, is never lengthened by the inter- 
