Fertilization in Pimts Strobus. 447 
in the present discussion of the maturation of the egg, for, 
in our material, these figures, and also Blackman’s Fig. 11, 
would be interpreted as representing disintegration stages. 
Every step has been repeatedly traced from the ordinary 
nuclear reticulum to nuclei which can scarcely be distinguished 
from the surrounding cytoplasm, and then to archegonia which 
appear perfectly normal, except that no nuclei can be 
demonstrated within them. It is a well-known fact that 
the number of seeds derived from a Pine cone is very small 
in comparison with the number of ovules formed in a given 
cone. An examination of fresh material shows that develop- 
ment may cease at any point between the early stages in the 
formation of the ovule and the last steps in the ripening 
of the seed. This cessation of growth does not at once 
become apparent, and so cannot be avoided, in its earliest 
stages, when one is putting up material for cytological work. 
Under such conditions, it is inevitable that, with a limited 
amount of material, the abnormal will be interpreted for the 
normal. 
The entire development of the archegonium in Pinus 
Strobus is passed through in about two weeks, probably 
not more than five days elapsing between the cutting off 
of the ventral canal-cell and fertilization. In Pinus montana , 
var. uncinata , these processes are apparently much more 
closely united in point of time, as the pollen-tube, in some 
cases, has reached the endosperm before the division of the 
central cell is completed (Fig. 33). 
Conjugation of the Sexual Nuclei. 
When the time for fertilization arrives, the apex of the 
pollen-tube is ruptured, and almost all its contents pass into 
the cytoplasm of the egg. The sperm-nuclei, still surrounded 
by a common mass of protoplasm ; the vegetative nucleus ; 
the stalk-cell ; a part of the cytoplasm from the pollen-tube ; 
and some of the starch-grains from the male gametophyte 
can all be distinctly recognized in the upper part of the 
oosphere (Figs. 39-42). Dixon (’ 94 ) noted the passage into 
