228 
Notes on Recent Literature . 
5. terrestris and S. californicus growing in their natural habitat 
near Chartres. An examination of 81 groups of young plants, gave 
43 with each two male and two female plants; in 21 other cases the 
differences from the usual rule were easily explained by the unions 
of tetrads in pairs, or by the fusion during growth of separate 
thalli, or by the sterility of some of the thalli. Thus 64 of the 81 
groups showed clearly that the separation of sex takes place at the 
time of spore-formation ; in 13 other cases the distribution of sex in 
the groups could not be made out. Four cases, however, remained 
outstanding, and clearly departed from the rule. One group showed 
5 female and 3 male, another 3 male and 1 female, while in two 
others there were 3 female and 1 male. The exceptions are clearly 
so few that the segregation of sex at the meiotic divisions of the 
spore-mother-cells must be accepted as a general rule in the dioecious 
Bryophyta. 1 
On the observations on Sphcerocarpus the author bases an 
interesting discussion on the nature of sexual differences in plants 
and the point in the life-history at which the male and female 
tendencies are separated. It is clear that the sexual tendencies are 
not always separated by the meiotic division. Some Bryophyta are 
monoecious and even in dioecious mosses when diploid gameto- 
phytes are raised from protonema caused to develop from the 
sporogonium, such gametophytes bear both kinds of sexual organs, 
as E. and E. Marchal showed. We find a similar condition in many 
homosporous Pteridophyta; a separation of the sexual tendencies 
only takes place in the hermaphrodite prothallus before the 
formation of antheridia and archegonia. In the heterosporous 
Pteridophyta we have the separation of the sexual tendencies 
shifted back from the haploid to the diploid generation, to the time 
of formation of the microspore-mother-cells and megaspore-mother- 
cells. Here again it is clear there is no analogy with Sphcerocarpus, 
for the separation of the sexes takes place earlier than, and inde¬ 
pendently of, the meiotic division. The dioecism of the heterosporous 
diploid generation of the higher plants thus presents itself as a 
problem distinct from that of Sphcerocarpus. Correns and Noll 
both agree on the view, based on hybridizing experiments, that the 
eggs of the dioecious Phanerogams possess a female tendency. For 
the male products Correns holds the view that half possess male 
and half female tendencies. Noll, on the other hand, holds it 
probable that the male cells all possess a male tendency, but in 
different degrees, half possessing it strongly, half weakly. In the 
first case it is dominant over the fernaleness of the egg, and a male 
individual would result on such a fusion ; while in a fertilisation 
brought about by a male cell of the second class, the femaleness is 
dominant over the weak male tendency and a female individual 
results. Phylogenetic considerations have led Strasburger to the 
same conclusions as those reached by Noll. The reduction-division 
in the microspore-mother-cells can segregate male tendencies of 
unequal strength, but clearly does not separate maleness and 
femaleness; that separation has taken place earlier. The difference 
in strength of the male tendency in microspores and pollen-grains 
1 It is interesting to note that Strasburger now definitely gives 
his adherence to the term meiosis as suitable for international 
use. 
