Wilson.—Sex Determinatio?i in Mnium hornum . 437 
similar results. It is noteworthy that the percentage of bisexual axes pro¬ 
duced has no relation to the sexual condition of the parent; the protonema 
derived from a bisexual individual does not produce a larger number 
of bisexual axes than one produced from a male or female plant; in all 
cases a large proportion of male axes are produced. 
Several instances of the occurrence of hermaphrodite axes in various 
dioecious mosses have been mentioned above, and these render it question¬ 
able whether the proportion of bisexual individuals in the aposporous 
generations is really higher than that occurring in normal plants. If, as the 
result of further research, it is established that the increased proportion does 
exist, the possibility that it is brought about by the disturbance in the 
metabolic processes caused by the abnormal number of chromosomes 
present in each cell must be considered. It has been shown by El. and 6m. 
Marchal ( 11 ) that the presence of the diploid number of chromosomes 
results in the increased size of the organs, cells, and nuclei of the apospo- 
rously produced plants, and it appears to be possible that it has also 
had a disturbing influence on the sexual condition of the individuals. 
Strasburger ( 15 ) in discussing the results obtained by 6l. and Em. 
Marchal points out that the work of Philibert is of importance. Philibert 
( 13 ) found that in Homalothecium fallax , Camptothecium lutescens , and 
Fissidens bryoides protonemata derived from dying leaves and lower parts of 
the female plants produced small male plants. These mosses are normally 
dioecious, but it is obvious that in these cases no complete sex separation 
can have taken place. The peculiar distribution of sexual organs in Mnium 
cinclidioides described by Milde in 1865 (12a) must also be considered here. 
This species is normally dioecious, but in certain apparently sterile axes 
Milde found small bud-like structures each containing antheridia and 
archegonia. In this case also sex separation must therefore be incomplete. 
If the conclusions of 6l. and 6m. Marchal are accepted, it must 
necessarily follow that in the Musci each kind of gamete bears only 
the potentialities of its own sex. There is, however, no direct evidence 
that this is the case in the Bryophyta. No instances of apogamy are at 
present known in this group, and investigations as to the sexual condition 
of particular species are very few in number. Apart from the work of 
6l. and 6m. Marchal no researches of this kind have been carried out in the 
Musci. Among the Hepaticae Sphaerocarpus has, however, been the subject 
of a somewhat similar investigation. Strasburger ( 16 ) quotes the results 
obtained by Ch. Douin, who examined the sexual condition of the plants 
arising from the four spores of each tetrad in two species of this genus. In 
both 5 . terrestris and 5 . californicus the spores of each tetrad remain 
in contact, and the resulting plants are in consequence found in groups 
of four. Eighty-one of these groups were examined, and in sixty-four 
of these two male and two female plants were found ; in thirteen cases 
