19 
Embryo of Sequoia sempervirens . 
Pinus Str obits, in Taxodium by Coker (1900), and in Cephalotaxus by 
Arnoldi (1900). It therefore happens that at the time of fusion of the male 
and female nuclei in many Conifers the archegonium contains both male 
cells as well as the stalk- and tube-nuclei. In his recent work on Thuja , 
Land (1902) finds that the tube- and stalk-nuclei may sometimes enter the 
egg, but in the majority of cases they do not enter at all, but become dis- 
organized in the space above the archegonium complex. Compared with 
these other Conifers, Sequoia sempervirens stands unique, in that only the 
nucleus and a very small amount of cytoplasm of the male cell enters the 
egg. Only the two sex-nuclei are present in the egg at the time of fusion. 
As the male cell passes through the narrow canal of the neck, it 
immediately advances toward the egg-nucleus. As shown in Fig. 31, it 
has a long-drawn-out appearance. As it advances, the forward portion 
becomes rounded and very much wider than the long tapering hinder 
portion. While in this condition it first flattens against and then pushes 
in the membrane of the egg-nucleus. The long tapering end now draws 
in, and the male nucleus is more or less spherical. At the time of their 
fusion the male and female nuclei are of equal size, and in this respect differ 
from those in Tsuga and Pinus (Murrill, 1900; Blackman, 1898), where 
the male is much smaller than the female. Each cell has a large nucleolus, 
and the chromatin is in the form of small granules suspended in a regular 
network of linin threads. The chromatin in the female nucleus appears 
to be more finely granular than in the male, and consequently the male 
stained more deeply with safranin. 
In Pinus the conjugation of the sexual nuclei has been worked out 
with considerable detail by Blackman (1898), Chamberlain (1899), and 
Ferguson (1901). According to these writers, the membranes of the 
sexual nuclei remain intact for some time after the penetration of the 
male into the female. Blackman further finds that the first segmentation- 
spindle begins its formation before the male and female nuclei lose their 
identity. This has been partially confirmed by Chamberlain (1899), an d 
Ferguson (1901), in Pinus , and by Woycicki (1899) in Larix , who were 
able to distinguish the male and the female chromatin as distinct groups 
inside the walls of the female nucleus. 
In Sequoia sempervirens the behaviour of the conjugating nuclei differ 
slightly from that described above for Pinus and Larix. As the male 
nucleus pushes into the female it becomes only partially surrounded by 
the membrane of the latter. This is no doubt due to the fact that the 
conjugating nuclei in Sequoia are of equal size. The membrane separating 
the two nuclei apparently breaks down much earlier than in Pinus. The 
chromatic contents of the two nuclei flow together, forming a common net- 
work in which the male and female elements can no longer be distinguished. 
The fusion-nucleus thus formed is very large and occupies a central 
