142 
Notes. 
formation of the archegonia, at a stage when no cells have as yet been 
formed within the embryo-sac, but only free nuclei imbedded in 
common protoplasm 1 . 
Although all the other Gymnosperms examined proved to be less 
favourable than Ceratozamia for the study of the karyokinesis in the 
embryo-sac, it was nevertheless ascertained that in Tsuga canadensis , 
Larix decidua , and in Ephedra Helvetica the reduction occurs in the 
earliest stages of the development of the endosperm, whereas the nuclei 
of the cells of the nucellus and of the integument have the full number 
of chromosomes. It is therefore in the highest degree probable that 
the reduction in the number of chromosomes is effected during the 
formation of the embryo-sac, and persists through the whole female 
gametophyte (endosperm), including the oosphere. 
The writer has also found that in the Gymnosperms, as in the 
Angiosperms, a similar reduction takes place in the mother-cells of 
the pollen and persists through the whole male gametophyte. 
We are thus brought face to face with the fact that, so far as 
investigation has been carried at present, the sexual and the asexual 
generations in the Gymnosperms differ in that the nuclei of the latter 
contain twice as many chromosomes as do those of the former. It 
might even be possible to extend this generalisation so as to include 
the Angiosperms, were it not that Guignard 2 has observed that, in the 
Lilies, the antipodal nucleus possesses a greater number of chromo- 
somes than does the sister-nucleus at the micropylar end of the 
embryo-sac ; a greater number, in fact, than the primary nucleus of 
the embryo-sac contains 3 . 
Passing now to the higher Cryptogams (Pteridophyta and Mus- 
1 As the discovery of the attractive spheres (centrospheres) in plants is very recent, 
it may be mentioned that the young endosperm of Ceratozamia is a most favourable 
object for studying them. The writer has always been able to find them here with- 
out much difficulty. He has also seen them in Taxus, Larix , and several other 
Gymnosperms, also in Leucojum , Paeonia , Aconitum, &c. 
2 Guignard, Nouvelles Etudes, loc. cit. pp. 188 and 255. 
3 It will be well to bear in mind that the antipodal cells of the Lilies are of 
a very transitory nature, degenerating almost as soon as formed, and that irregu- 
larities in rudimentary organs are not uncommon. As a matter of fact the number 
of chromosomes in the antipodal cells of the Lilies, although it would appear to 
be always greater than twelve, is not constant, varying between sixteen and twenty- 
four. The writer thinks it not improbable that in many other Angiosperms the 
antipodal cells will be found to contain the reduced number of chromosomes. 
Further researches alone can settle this question. 
