1 66 Lawson . — The Gametophytes and Embryo of 
and descend slowly in the wake of the tube nucleus. In their movement 
down the tube both these structures enlarge to three or four times their 
original size. But the body-cell — which during these stages was always 
found in advance of the stalk-cell — increases in size at a much greater rate 
than the latter, so that before they have advanced very far into the tube the 
one is more than twice the size of the other. These conditions are indicated 
in Fig. 5. 
Owing to the large number of pollen-tubes that were found growing in 
the upper chamber of the micropyle, and also owing to the fact that there 
was no tissue in the way to offer resistance to their growth, the tubes 
elongated towards the nucellus in a more or less irregular fashion. These 
circumstances made it impossible to obtain a section showing the full length 
of any one tube. On comparing the series of sections from which Fig. 4 was 
drawn it was evident that the tubes folded about each other in such a fashion 
as to form a complex tangle as they elongated. Fragments of at least five 
different tubes are shown in Fig. 4. Fig. 6 represents a portion of a section 
of a young tube with the body-cell descending towards the tip. It will be 
observed from this figure that the nucleus of the body-cell has enlarged 
enormously. The entire cell becomes very much elongated with the 
nucleus in advance of the drawn-out cytoplasm. At this time the mem- 
brane enveloping the body-cell becomes exceedingly thin, and in many cases 
could only be distinguished by careful focusing. Its location, however^ 
could always be made out as the line separating the coarse granular cyto- 
plasm, characteristic of the body-cell, from the more delicate and less dense 
cytoplasm of the tube. 
In Fig. 7 is represented the condition of the body-cell at a time when 
the tip of the tube has traversed about half the length of the micropylar 
canal. As it was possible to obtain only short segments of the pollen-tubes 
in longitudinal section I was unable to determine the relative positions 
of the stalk- and body-cells at this time. There was some evidence, how- 
ever, that the stalk-cell was now in advance of the body-cell as happens in 
Pinus (Ferguson, ’04), but with so many segments of different tubes in the 
micropyle one could not be certain that one was following the same tube in 
serial sections. 
The actual division of the body-cell was not observed, but after a study 
of the chromatin and the cytoplasm immediately surrounding the nucleus, 
it seemed quite certain that this division takes place before the tip of the 
pollen-tube reaches the nucellus. In Fig. 7 the nucleus is represented very 
much enlarged — its diameter being nearly equal to the width of the pollen- 
tube. A large, deeply-staining nucleolus was always present, and the 
chromatin at this time was in the so-called reticulum stage. This reticulum 
seemed to be made up of very delicate threads which crossed and anasto- 
mosed with one another in such a fashion as to give the appearance of 
