128 
Arlow Burdette Stout 
Meleagris, Najas major, Triticum vulgare, Tradescantia virginica, Vera- 
trum album, Convallaria majalis, Leucojum aestivum, Tamus communis, 
Canna indica, Epipactis palustris), and finds that in every case the ge- 
nerative cell is cut off by a cell plate at the periphery of the microspore. 
It is then set free and migrates into the cytoplasm of the vegetative cell. 
I have not found the early stages of its formation in Carex aquatilis, but 
its crescent or spindle shaped form (fig. 32) as it lies in the cytoplasm 
is commonly shown in my preparations and suggests that it is formed 
in the usual way and not by free cell formation. 
The vegetative nucleus becomes quite large and the chromosomes 
in it lie scattered in series about the periphery with much the appearance 
observed in resting root-tip nuclei. The generative nucleus gradually 
becomes more spherical. Düring these changes the pollen grain enlarges 
considerably and its central portion is occupied usuaUy by one or more 
large vacuoles. This increase in size will be appreciated from a com- 
parison of figures 30 and 33. The generative cell and the vegetative 
nucleus now usually lie near each other and near one side of the pollen 
grain. The chromosomes are conspicuous, their number is plainly that 
of the haploid nuclei. The drawing shown in figure 34 is from a section 
through a generative nucleus in late prophase. The chromosomes are 
spherical bodies connected in a single continuous series, in appearance 
and arrangement quite siniilar to that of the prophase of the division 
of diploid nuclei (compare fig. 34 with fig. 11). In the early stages of 
reconstruction the nuclei appear as shown in figure 35. Although these 
nuclei are very smaU the chromosomes are sharply differentiated at aU 
stages. Each male cell, when fully formed, possesses a considerable 
aniount of cytoplasm with a clearly defined membrane, as is shown in 
figure 36. The germ ceUs are fuUy formed before the pollen grains are 
shed from the anther. The vegetative nucleus of the pollen grain is 
spherical in shape and it usuaUy lies near the large end of the poUen 
grain. The two male cells lie embedded in the cytoplasm of the vege- 
tative cell. Their nuclei are spherical vdth the individual chromosomes 
as noted rather clearly defined. The central part of the pollen grain 
is coarsely vacuolated and the germ cells lie near the walls of the pollen 
grain. Usually they are not far from the vegetative nucleus and are 
often on opposite sides of it. 
The vegetative nucleus of the microgametophyte is of about the 
same size as the nuclei of the somatic cells in the root tip, as will be seen 
from a comparison of figures 33, 35, and 36 with figure 4. The male 
nuclei are smaller. The chromatin in them is present, however, as distinct 
