Fertilization in Pinus Strobus. 443 
power, the cytoplasm of the mature egg appears dense and 
finely granular ; the ‘ proteid vacuoles 5 do not seem to differ 
materially from the protoplasm in which they are embedded ; 
and many deeply staining granules are scattered throughout the 
cell. With greater magnification, however, a very beautiful, 
granular reticulum becomes apparent ; there is no suggestion of 
the alveolar structure described by Butschli (’ 94 ). At times 
this reticulum is everywhere crossed by short fibres, which 
have no definite arrangement, and are, apparently, not confined 
to any fixed period in the history of this cell (Fig. 30). The 
spheres in the outer and basal portions of the cytoplasm are 
resolved into very complex structures which, although they 
simulate the appearance of nuclei, could never be mistaken 
for such bodies by one familiar with cell-structures (Figs. 33 
and 34). 
Immediately preceding fertilization a cavity appears in the 
egg- cytoplasm, just beneath, or in the near vicinity of, the 
neck-cells (Figs. 12 and 38). In some cases this opening 
may not arise until the instant of fertilization. This cavity, 
which was thought by the earlier writers to represent the 
lower portion of the pollen-tube within the oosphere, has been 
explained by Blackman (’ 98 ) as due to the sudden inrush of 
the contents of the pollen-tube, and by Arnoldi (’00) in 
Cephalotaxus , as caused by the downward movement of 
the conjugation-nucleus. Shaw (’ 98 ) suggests that the con- 
cavity in the upper part of the egg of Onoclea , just prior to 
fertilization, may correspond to the receptive spot ; and there 
is every evidence that in Pinus Strobus this opening in the 
cytoplasm represents the last act of the egg in its preparation 
for the reception of the sperm-nucleus. If it were formed 
by the movement of nuclei or other bodies through the 
protoplasm, we should expect the cytoplasm to draw together 
again, as during the downward movement of the egg-nucleus ; 
but, in reality, this opening persists throughout the entire 
later history of the archegonium (PI. XXV, Figs. 77 and 78). 
The regular, clear outline of this cavity, together with the 
fact of its presence in the unfertilized as well as the fertilized 
