Antkoceros laevis. 
507 
genous tissue or the young spores undergo development, it 
would merely increase the difficulty of demonstration in the 
case of any particular growth. In the majority of the pieces 
of young sporogonia experimented with, the young spores 
simply disintegrated without any attempt at further develop- 
ment. In one case, however, growth had taken place within 
the spore-sac leading to the presence of young plants consist- 
ing of a few cells ; from this single example it was impossible 
to decide with certainty whether these were referable to young 
spores or to spore-mother-cells. 
The small number of specimens obtained from this culture 
did not afford material for the study of the cytological changes, 
which may occur in the cells destined to give rise to a gameto- 
phyte. The frequency with which the new growths start from 
single sterile cells of the sporogonium might make this and 
similar cases of apospory suitable for such observations. 
Even in the absence of observations on the behaviour of the 
nucleus, certain considerations on the point of view, from 
which the phenomenon of apospory is best regarded, are 
suggested by this case, and may be briefly referred to without 
entering on any general discussion of apospory. 
In the normal life-history of such a plant as Antkoceros the 
fact that the fertilized ovum gives rise to the sporophyte and 
the spore to the gametophyte must be regarded from two 
points of view. In the origin of both generations the start is 
made from a single cell (zygote, spore) and these cells in the 
two cases have had very different histories. The zygote has 
arisen by the fusion of two cells, while the formation of the 
spore is preceded by the reduction of chromosomes in the 
spore-mother-cell. But it is not sufficient in considering the 
remarkable fact — that these two sorts of reproductive cells in 
the same species give rise to distinct and very different stages 
in the life-history — to note their different origin. The con- 
ditions under which they undergo their further development 
are also very different in the two cases. The spore, separated 
from the parent plant, falls on the ground, and under suitable 
conditions of moisture, warmth, and illumination develops 
