THE MORPHOLOGY AND AFFINITIES OF GNETUM 1 55 
condition. The tube nucleus is slightly larger than the generative 
nucleus but is much less dense and has a very distinct nucleolus. In 
most preparations it is impossible to distinguish the cytoplasm of the 
generative cell from the general cytoplasm of the spore. But in well- 
stained sections the generative cytoplasm is seen as a narrow lighter 
band surrounding the generative nucleus, the whole cell being only 
slightly larger than the tube nucleus. The generative nucleus is very 
dense and deeply staining. Very soon the generative cell divides to 
form a small stalk cell and a body cell (fig. 30). In this condition the 
pollen grain is shed, and consequently at polHnation time the gamet- 
ophyte consists of a tube nucleus in the general cytoplasm, a body 
cell and a stalk cell. The tube nucleus is distinguishable by its 
greater size, lighter appearance and conspicuous nucleolus. It is 
very often difficult to see that the body nucleus and stalk nucleus are 
each surrounded by its own cytoplasm. The body nucleus is smaller 
than the tube nucleus and very dense. The stalk nucleus is very 
small and dense. Frequently the stalk and body nuclei appear to be 
in the same cytoplasm (fig. 31). 
It is particularly easy to w^atch the growth of the pollen tube 
because as previously stated the pollen grains frequently germinate 
in the style. The exine is thrown off as usual and the cavity of the 
style in later stages frequently contains many of these outer coats. 
The intine grows out into a tube at the point nearest the tube nucleus. 
Figure 32 represents a tube which has branched though far from the 
nucellus. The tube nucleus with its conspicuous nucleolus is next 
to the branched end. Back in the pollen grain proper are the body 
and stalk cells, each with its own cytoplasm. As the tube grows the 
tube nucleus and body cell pass out into it (fig. 33). The stalk nu- 
cleus seems invariably to stay behind in the old grain. There it re- 
mains for a long time until finally it degenerates. Figure 35 shows 
the tip of a nucellus with many pollen grains which have germinated 
and sent tubes far down towards the embryo-sac. In all cases the 
tube nucleus and body cell have passed down the tube but the stalk 
nucleus has remained in the old pollen grain. Some of them have 
begun to disintegrate. Old germinated pollen grains, whether in the 
style or on the nucellus usually show remains of this stalk nucleus. 
So far as I am aware this behavior occurs in no other Gymnosperm. 
It seems to be a step towards the complete elimination of the stalk cell. 
The body cell never divides until it is in the pollen tube. Figure 
