Notes . 
141 
vegetative cells ; and the further inference might be drawn that the 
essential difference between vegetative (or somatic) and reproductive 
cells is indicated by the smaller number of chromosomes in the nuclei 
of the latter. But, though this course of reasoning may seem obvious 
enough, it is a question if it be the one which is really indicated by the 
facts. It must be borne in mind that the spore is the first stage of the 
sexual generation (gametophyte) : hence when, as in the case of the 
Lily mentioned above, the same reduced number of chromosomes is to 
be found in both the embryo-sac (macrospore) and the oosphere on the 
one hand, in the pollen-grain (microspore) and the generative cells of 
the pollen-tube on the other, all these cells belonging to the sexual 
generation, it seems to be suggested that the reduced number of 
chromosomes in the nucleus is a feature which is peculiar, not to the re- 
productive cells, but to the whole sexual generation (gametophyte). This 
view of the matter is supported by the fact that during the division of 
the progamous nucleus of the pollen-grain we likewise find the reduced 
number of chromosomes, as was established by the three authors 
already mentioned. 
In order to test the value of this latter hypothesis, it is essential that 
plants should be examined in which a greater number of cell-genera- 
tions should intervene between the spore and the sexual reproductive 
cells ; plants, that is, in which the gametophyte has a more pronounced 
individuality than it has in the Angiosperms, where only three 
cell-generations intervene between the development of the embryo-sac 
and that of the oosphere. 
Thus, in the Gymnosperms a whole complex of cells, the endosperm, 
is formed in the embryo-sac before the female organs make their 
appearance. If now these cells show the same reduction in the number 
of the chromosomes in their nuclei as do the embryo-sac on the one 
hand, and the oosphere on the other, this reduced number will be 
proved to be a characteristic, not of reproductive cells only, but of the 
whole sexual generation. 
For the investigation of this point Ceratozamia mexicana offers most 
suitable material, the nuclei being large and the number of chromo- 
somes small. In the various parts of the asexual generation (sporo- 
phyte), in the nuclei of the young leaf, in those of the nucellus and its 
integument, the number of chromosomes is sixteen. In the developing 
gametophyte, the young endosperm, on the other hand, each nucleus 
contains but eight chromosomes, and this is the case long before the 
