12 Lawson . — The Gametophyies , Fertilization and 
’04), Sequoia (Lawson, ’04), Podocarpus (Coker, ’03), and probably Torreya 
(Robertson, ’04). It is an interesting fact that in all those forms so far 
investigated in regard to the ventral canal-cell, the membrane which 
separates the egg from the ventral nucleus has only been found in repre- 
sentatives of the Abietineae. This fact itself may not be of great im- 
portance, especially as there are many forms yet to be investigated. It 
seems to be significant, however, when we take it in connexion with the 
survival of the vestigial prothallial cells in the pollen-grain, for here too 
these vestigial structures are only found, so far as we know at present, 
in representatives of the Abietineae (the single exception being that of 
Podocarpus ). If the retention of such evanescent vestigial structures 
as the prothallial cells in the pollen or the membrane of the ventral 
canal-cell has any phylogenetic bearing, then we have an argument in 
support of the primitive character of the Abietineae as a group. 
Great care was taken to follow up the further history of the ventral 
nucleus. It remains in the neck region until the egg-nucleus moves down 
and takes a position in the centre of the archegonium and it then shows 
signs of disorganization. It completely disintegrates, and deeply-staining 
nuclear fragments of it were frequently observed just below the neck- 
cells. At the time of fertilization very little trace of it was left. By 
the time the ventral nucleus has become disorganized the egg-nucleus 
is found in the widest part of the archegonium (Fig. 27), and here, much 
enlarged, it remains until its fusion with the male nucleus. 
For a short time before and during fertilization the cytoplasm takes 
on an extraordinary modification. Peculiar dense centres of cytoplasm 
make their appearance and, as shown in Figs. 26, 27, and 28, they are 
arranged in a single row which extends from the egg-nucleus to the 
base of the archegonium. In a general way they have the appearance 
of asters, for from each of them the cytoplasm is arranged in a series 
of radiations. These radiations do not seem to be more fibrous than 
the rest of the cytoplasm but are peculiar in that they extend out from 
these definite centres. I am unable to understand the meaning of these 
structures, but they are a constant and striking feature of the mature 
archegonia. 
Fertilization. 
From our description above we have seen how the pollen-tube pushes 
its way through the nucellar tissue until it reaches the cavity in the female 
prothallium immediately above one of the archegonia. At this period of its 
development the tube contains the stalk- and tube-nuclei, lying freely in the 
cytoplasm, and the two sperm-nuclei, both enveloped in the old wall of the 
body-cell. All of these structures are at the tip of the tube, which has 
become greatly distended. In some cases it was found that the contents of 
