: 
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Eee as (gu eae Se a ee er 
a eae : 
1906) YAMANOUCHI—POLYSIPHONIA VIOLACEA 435 
reasonable to expect important differences in the position of the period 
of chromosome reduction. 
Origin of the tetraspore-—The simplest genera of the red algae, 
such as Lemanea, Batrachospermum, Chantransia, and Nemalion, 
have no tetraspores, but some of them have monospores, as in Chan- 
transia and Batrachospermum (including the Chantransia form). 
In these types the period of chromosome reduction may be associated 
with the carpospore, either just before its development or at the time 
of its germination. The monospores, then, in such genera are not 
vitally concerned with the life history, and indeed are present upon 
the gametophyte. The tetrasporic plant may have arisen by a sup- 
pression of the reduction phenomena in connection with the carpo- 
Spore, so that it germinates with the sporophytic number of chromo- 
Somes, producing a plant with this number, which consequently 
becomes at once a part of the sporophytic phase. The period of 
chromosome reduction would be thus postponed from the carpospore 
to a later period in connection with the newly formed plant. Such 
plants by developing tetraspores would end the sporophyte generation. 
It is quite possible that the first tetraspore mother cells corresponded 
to monospores on the sexual plants except that they had the double 
number of chromosomes, since such reproductive cells would very 
naturally become the seat of the delayed reduction phenomena. The 
resemblance in general morphology of the tetrasporic plants in the 
ted algae to the sexual plants would be expected, because they live 
under similar environmental conditions, and we have another illus- 
tration of Such similarity of gametophytes and sporophytes in the 
Dictyotaceae. 
Abnormalities of the nature of monospores.—It should be remem- 
bered that sexual plants (cystocarpic) of Polysiphonia occasionally 
develop an abnormality in the form of a cell resembling a monospore 
but having the same cell lineage as the tetraspore mother cell. This 
abnormality may indeed be a reversion to an ancestral type of mono- 
spore, that in the process of evolution has given place to the tetraspore 
mother cell, which is only found in the sporophytic generation. It 
may be, however, simply an exceptional condition without any 
Phylogenetic significance. 
