394 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
mother cells of the pollen and of the embryo sac. Guignard also 
(1889 and 1891) demonstrated these phenomena in Lilium and in the 
pollen mother cells of Ceratozamia, noting the eight double chromo- 
somes in the latter and other peculiarities of the first mitosis. Over- 
ton (1893) counted the same number of chromosomes in the female 
prothallus of Ceratozamia, while Farmer (1894) found four chromo- 
somes in the thallus and sexual reproductive cells of Pallavicinia, 
and eight in the seta and capsule. 
Later in the same year Strasburger, in a masterly address before 
the British Association, completed the proof of Overton’s suggestion 
(1893) that in the mosses and ferns also reduction takes place, as 
Overton puts it, ‘‘in the mother cells of the spores; that is, at the 
point of alternation of the generations.’ Strasburger, by com- 
paring his counts of chromosomes in the dividing spore mother cells 
of Osmunda with the number seen by Humphrey (figures published 
in 1895) in the tapetal cells, found the latter number about double. 
It is interesting to note also that the Osmunda slides used in this work 
were among the first paraffin sections used by Strasburger. 
From this correspondence of the hyerwort and fern mentioned 
with the seed plants in which reduction had been seen, Strasburger 
was led to predict the universal occurrence of this phenomenon of 
reduction in all plants that reproduce sexually. Concerning the 
phylogenetic origin of the reduction process Strasburger held that all 
plants (and animals) were primitively nonsexual and had a constant 
number of chromosomes. With the development of sexual repro- 
duction the initiation of the process of chromosome reduction avoided 
the evident disadvantage of repeated doubling of the chromosome 
number at each sexual fusion. This return from the double number 
formed in the zygote to the primitive ancestral number of chromo- 
somes he believed might occur at any point in the life cycle before 
the next fertilization. Strasburger then went on to emphasize 
the advantage of the sexual mode of reproduction, when once ac- 
quired, in allowing new combinations of parental strains in the 
offspring, and the disadvantage it had of producing so small a number 
of offspring. It is to meet this disadvantage, he suggested, in agree- 
ment with Bower, that the zygote of forms lke Coleochzte, mosses, 
ferns, and seed plants took over the function of multiplying the 
progeny by a sort of polyembryony—the formation of spores. The 
spore-bearing generation later in the evolutionary history became 
ultimately independent of the gametophyte, and at a still later period 
it not only produced two kinds of spores but also assumed the care 
and nutrition of the reduced female plant arising from the larger 
of the two kinds of spores. Thus, in Strasburger’s view, the primitive 
nonsexual generation is now represented in the archegoniates by 
only the sexual phase, which has gradually lost its power of asexual 
