120 BOTANICAL GAZETTE {AUGUST 
their enlargement and crowding upon one another produces such a 
complex that it is practically impossible to count the tubes except 
by their nuclear contents. The tubes which are on the periphery of 
the complex may be so crowded by the more interior ones as to 
remain quite narrow and their contained body cells may even be 
flattened by the pressure. 
The cytoplasmic contents of the tube become quite vacuolated 
early in the growth of the tube and in early stages contain a large 
number of starch grains, although these apparently disappear in 
the later stages. The cytoplasm is always more abundant near 
the growing end of the tube, but when the tube enlarges at the 
forward end the bulk of the cytoplasm remains more or less closely 
connected with the nuclei of the male gametophyte. Frequently 
in late stages the cytoplasm may contain accumulated masses, 
irregular in shape and densely staining, and these may even be 
discharged into the egg cytoplasm at the time of fertilization. : 
DEVELOPMENT OF MALE GAMETOPHYTE.—Soon after pollination 
the microspore begins to elongate, and the first division into tube 
and generative cells takes place within 10-12 days after pollination 
(fig. 16). This division results in two unequal cells (fig. 17), the 
smaller generative cell being held in the base of the grain by a 
_ plasma membrane, while the larger tube cell forms the elongating 
tube. The division of nuclear material is no doubt equal, but the 
tube cell nucleus soon becomes larger than the nucleus of the 
generative cell, the former becoming ellipsoid and retaining this 
shape tk the inder of its history. The cytoplasm of 
the generative cell is denser eG — of ihe tube cell. 
: ' As! ee aes, a 7. re ak 
: » the grow- 
a ing end, migrating rapidly be behind the tip of the tube ey iG, Os 
oe EB yen before the ‘generative coll divides, the tube cell nucleus has” 
usually gone some distance into the tube. The generative c sl ae 
: . enlarges, pushes out its tim ting 
_ found together in the basal par 
