230 BOTANICAL GAZETTE | OCTOBER 
During June and the early part of July the pollen tube con- 
tinues gradually to grow in diameter, increasing but slightly in 
length, until by the middle of July it has reached a diameter 
somewhat greater than the pollen grain, which at this time forms 
simply a cap over the proximal end of the tube (fig. 5). The 
generative and stalk cells have increased greatly in size and 
have pushed out of the pollen grain into the tube, but still 
remain attached. A careful search was made in the generative 
cells of material collected at various periods up to this time for 
the centrosome-like bodies or “attractive spheres” described by 
Hirase, but in no case was any indication of them discovered. 
In material collected July 20, however, the centrosome-like bodies 
were found for the first time (jigs. 5 and 6). There is consid- 
erable variation in the rapidity of development of different pollen 
tubes in fruits collected the same day, and it was only in the 
most advanced tubes that the centrosome-like bodies could be 
found atthistime. In material collected July 27 they were found 
in almost every generative cell examined. Two of the spheres 
occur uniformly in each generative cell and are located 
in the cytoplasm on opposite sides of the nucleus about midway 
between the nuclear membrane and the cell wall ( fig. 6). They 
are spherical and of uniform size, but are quite small, being only 
about 0.6 to 0.7# in diameter. They are very plainly distin- 
guishable, however, as they stain differently from the surround 
ing cytoplasm. The radiations of kinoplasm are at this time 
few in number and comparatively short. They are thick at the 
base where they join the so-called centrosome-like bodies and 
are reduced to a very fine point at the end. The generative cell 
in this stage is usually nearly spherical, being somewhat com- 
pressed on the side attached to the stalk cell. It varies in size, 
being commonly from 25 to 35min diameter. The nucleus 1s 
spherical, from 16 to 18m in diameter, and contains a nucleolus. 
Both the nucleolus and the centrosome-like body are stained 
bright red with saffranin in using the Flemming triple stain, a5 
in the case of the centrosome-like body and nucleolus of Zami2. 
During August the stalk cell and generative cell continue 
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