8 BOTANICAL GAZETTE [JULY 
Belajeff (’91, ’93) describes the stalk nucleus as passing the 
central cell as it wanders down the tube. Such a description 
could hardly be applied in Taxodium when the tube is at right 
angles to the axis of the spindle of the generative cell. The 
stalk nucleus is as near the tip of the tube as is the central cell, 
and they both wander down together until they reach the tube 
nucleus (fig. 22). It will be seen from fig. 26 that the three 
nuclei of the pollen tube can easily be distinguished at this 
stage. The stalk nucleus is smaller than the tube nucleus, while 
the protoplasm of the central cell is distinct from that of the 
pollen tube. The stalk and tube nuclei now advance slightly 
ahead of the central cell (fig. 23), and this relative position is 
retained by the three nuclei throughout the subsequent history 
of the pollen tube. In fig. 23 the stalk nucleus is still slightly 
smaller than the tube nucleus, but the structure of the two is the 
same. The male nucleus is very like the other two, its nucleo- 
lus being slightly smaller. 
_ The pollen tube proceeds to the prothallium without inter- 
ruption; the growth, however, is much slower in the upper part 
of the nucellus than in the lower. No particular tissue of the 
nucellus tip is set apart to nourish or guide the pollentube. All 
of its cells contain more or less starch, but there is no grouping 
_of starch in definite areas. The pollen tube may reach. the 
megaspore before the formation of a cellular prothallium (fg. 
25). So early an approach of the pollen tube to the sprouting 
megaspore has not been described in any other case, so far as 
I am aware. Jager (’99) gives one figure of Taxus baccata 
showing a pollen tube almost in contact with a young prothal- 
lium, and I have found that in Taxus baccata canadensis the 
pollen tube may reach the level of the megaspore before the 
latter has divided even once. One case was found in this plant 
where the pollen tube has grown against and badly compressed 
-the megaspore before the latter had advanced far beyond the 
sixteen-cell stage. It was so completely crushed that the stage 
could not be exactly determined. 
Fig. 26 gives the structure of the contents of the pollen-tube 
at a slightly later stage than fig. 25. The two free nuclei are 
