Fertilization in Pimis Strobus . 437 
plane (PI. XXIII, Figs. 3, n,and PI. XXIV, Fig. 40); in rare 
instances, the four cells divide by periclinal walls, when the 
eight cells which compose the neck of the archegonium are dis- 
posed in two tiers of four cells each (Fig. 20). This last seems 
to be the normal condition in Pinus austriaca and P. rigida , 
and is that figured by Blackman for Pinus sylvestris. 
At first the growth of the central cell is not followed by 
a corresponding increase in the amount of protoplasm ; and 
hence its cytoplasm early presents a very vacuolate appear- 
ance. There may be one large, irregular, central vacuole ; 
or delicate strands of cytoplasm may extend out from the peri- 
pheral layer of the protoplasm, forming vacuoles of various 
sizes. But, as the central cell continues to enlarge, its cyto- 
plasm begins to develop more rapidly, many strands extend- 
ing out into and across the vacuoles ; thus the size of the 
vacuoles is decreased while their number is greatly increased. 
The central vacuole, if present, may persist for a consider- 
able time, or it may be replaced at once by smaller vacuoles 
(Figs. 4 - 7 ). Gradually the cytoplasm becomes more dense ; 
and the vacuoles, receding from the periphery of the cell, 
especially from its base and sides, disappear last from its 
upper portion (Figs. 8 and 9). When the ventral canal-cell 
is cut off the vacuoles have nearly or quite been replaced by 
a finely granular cytoplasmic reticulum, in which a greater 
or less number of larger, more deeply staining granules are 
embedded. These granules are frequently surrounded by 
a clear court into which the protoplasmic network has not 
extended. The number of the so-called proteid vacuoles is 
usually small at this time (Fig. 10). 
The nucleus of the central cell attains full size very soon 
after its formation. It has a delicate, more or less interrupted, 
reticulum, and is characterized by a large, vacuolate nucleolus 
which invariably occupies a central position ; one or two 
smaller nucleoli may also be present. This nucleus always 
remains close beneath the neck cells, and is more or less 
concave on the side towards these cells (Figs. 4-9, 13, 14, and 
16). Although, as Blackman has pointed out, the vacuolate 
G g 2 
