30 Dixon. — Fertilization of 
for Gymnosperms ‘ that it is 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 same writer also found that in the Gymno- 
sperms, as in the Angiosperms, a similar reduction takes place 
in the mother-cells of the pollen and persists through the whole 
male gametophyte. 
In this connection it became interesting to study the in- 
stances of karyokinesis exhibited in the nuclei of the endosperm 
and the various tissues of Pinus. The small size of these 
nuclei, however, rendered the counting of the chromosomes 
very difficult ; nevertheless I have endeavoured, by multiply- 
ing my observations and by making careful drawings of the 
karyokinetic figures observed, to render my results reliable. 
From these drawings I found that the dividing nuclei of the 
cells of the nucellus, in those cases where the chromosomes 
could be counted, possess 1 6 chromosomes: Fig. 20 includes 
examples of the sketches made. In most cases it is best to 
draw those nuclei which one can view from one of the poles, as 
in them the chromosomes appear more widely separated from 
one another. The nuclei of the cells of the integument possess 
16 chromosomes and perhaps rarely 24. On examining then 
the young endosperm, I found that in nuclei taken from its 
middle and lower portions there were only 8 chromosomes, 
Fig. 21. Thus, so far, my observations on Pinus agree 
with those of Overton on other Gymnosperms. However, in 
pursuing my examination, I was surprised to find that, in 
sections made through the endosperm about June 19, which 
showed the archegonium and oosphere already formed, the 
cells forming the wall of the archegonium, which are much 
larger and have larger nuclei than the surrounding cells of the 
endosperm, possess usually a larger number of chromosomes -: 
the chromosomes in their nuclei are widely separated and are 
consequently easily counted with certainty. The prevailing 
number of chromosomes in these nuclei was not 8 but 12 ; 
I also found some cells with 24. Fig. 22 shows 4 cells from 
