156 
WALTER P. THOMPSON 
33 shows a tube in which the cell is just entering the nucellus. The 
tube nucleus is down at the tip of the tube. It will be observed that 
the body cell is undivided. Unfortunately I have never seen its 
division, but by the time it is half way through the nucellus it always 
contains two nuclei, consequently the division must occur in the upper 
part of the nucellus. It is usually impossible to see in my preparations 
that there are two distinct male cells. Generally I can see only two 
nuclei lying in a common cytoplasm (fig. 34). In favorable sections, 
however, one can see that this cytoplasm is divided into two by a 
delicate membrane (fig. 40). It may be that in all cases there are two 
distinct male cells but this I am not prepared to say. In the lower 
part of the nucellus the tube nucleus and male cells lie side by side, 
with the former in advance. Against the sac the tube nucleus is 
found at the side of or behind the male cells. The tube nucleus is 
always larger than the other nuclei and has a, prominent nucleolus. 
There is no difference in size between the male nuclei or cells. 
The most notable points in this gametophyte are (i) the absence 
of prothallial cells, (2) the germination of the pollen grains in the 
style as well as on the nucellus (3) the retention of the stalk cell in 
the pollen grain and (4) the division of the body cell in the nucellus. 
The first three points bring the male gametophyte of Gnetum very 
close to that of Angiosperms. 
8. Female Gametophyte 
As previously stated two or three megaspores usually develop into 
embryo-sacs. Each of these functioning megaspores is descended 
from a difi^erent mother cell. Figure 25 shows a four-nucleate em- 
bryo-sac and alongside it a megaspore derived from another mother 
cell. At the end of the sac and of the undivided megaspore are the 
sister megaspores which will not function. 
The subsequent divisions in the gametophyte take place in the 
usual Gymnospermic fashion. A vacuole soon appears in the center 
of the developing sac and the protoplasm and nuclei become confined 
to a parietal layer. Figures 36 and 37 illustrate the conditions found 
in the young sac, the latter figure also showing the typical appearance 
of two sacs in one nucellus at this stage. Very often the vacuole 
appears first at the upper end of the sac (fig. 38) and gradually ex- 
tends downward. In any case the upper end always becomes larger 
