284 Lawson.-— The Gametophytes and Embryo of the 
which they pass. All of the tubes penetrate the tissue near the apex of 
the nucellus. In no case was I able to find any of the tubes growing down 
between the nucellus and the integument, as so commonly occurs in Sequoia 
senipervirens (Lawson, ’ 04 ). 
Just previous to the penetration of the pollen-tube into the nucellar 
tissue, the generative nucleus enlarges and prepares for division. That this 
division occurs when the pollen-tube is very young was shown by the fact 
that in material collected during the second week in May, when the tube 
had penetrated but a very short distance into the nucellus, the body-cell 
and stalk-nucleus were completely organized. The body-nucleus was easily 
distinguished from the stalk-nucleus because of its greater size, and also 
because it very soon becomes surrounded by a cell membrane. The young 
tube at this time thus contains the large body-cell and the stalk- and tube- 
nuclei — the latter lying freely in the tube-cytoplasm. The body-cell is at 
first distinctly oval in form, and its long axis lies parallel to the long axis 
of the tube. Its nucleus is quite three or four times the size of the tube or 
stalk-nuclei. The latter structures are almost equal in size, and it is only 
from their position that they may be distinguished from one another ; they 
are, however, always found in advance of the body-cell. The appearance 
of the body-cell, from material killed May 31, is shown in PL XXIV, Fig. 6 . 
It will be seen that the cell is not so much oval in form as in earlier stages, 
and that its cytoplasm is very granular — containing more starch and other 
food substances than the tube-cytoplasm. 
By June 1 the tube has completely penetrated the nucellus. Meantime 
the female prothallium has been developing rapidly, and the archegonia are 
fully organized and nearly ready for fertilization by the time the tip of the 
tube reaches the archegonial chamber. During its entire growth the con- 
tents of the tube are always found at the tip. Just about the time the 
archegonial chamber has been reached the body-cell divides, and as a result 
of this division two distinct male cells of equal size are formed. Fig. 6 
represents the body-cell preparing for division. Fig. 7 represents the two 
male cells very soon after they have been formed. Fig. 6 was drawn from 
material killed May 31, and Fig. 7 June 1. As may be seen from Fig. 7, 
the two male cells are not quite spherical in form, but each of them becomes 
spherical as soon as they separate from each other and before the arche- 
gonia have been reached. It will also be observed that the nucleus of each 
male cell is very large, with a single conspicuous nucleolus, and the 
chromatin, in the form of small, uniform granules, suspended on a network 
of linin. 
The organization of two male cells of equal size seems to be a constant 
character of the Cupressineae (and I consider Taxodium and Cryptomeria 
as members of this group). The only exception which has so far been 
recorded is that of Cupressus Goweniana , in which Juel (’ 04 ) describes the 
