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DUNCAN S. JOHNSON 
massing of the chromatin threads. This is first seen over the area of con- 
tact, and then, as the walls between the two nuclei disappear, the chro- 
matin becomes especially abundant in a ring about the opening through 
the perforated wall (figs. 87, 93, 94). Thus the chromatin reticulum 
does not appear to degenerate over the surface of contact, but opens 
out and comes to lie chiefly on the surface of the new nucleus. Part 
of the chromatin may, for a while after fusion, be found in the interior 
of the fusion nucleus. Finally the composite chromatin net comes to 
be pretty evenly distributed over the surface of the large endosperm 
nucleus. This reticulum may at first show meshes of very different 
sizes in different parts. These correspond in size to the different sizes 
of mesh seen in the different contributing nuclei before fusion. They 
indicate clearly that the choromatin contributed by each fusing nucleus 
maintains its identity for some time at least, in the primary endosperm 
nucleus so produced (fig. 84). Whether the smaller of these fusing 
nuclei play an equal part with others in the later activity of the fusion 
product was not determined. The fusion of nucleoli does not occur as 
quickly, is not carried as far as that of the nuclei, and there are always 
several, often 6 or 8 nucleoli in the endosperm nucleus. The number 
of these nucleoli present and the size of some of them indicate that the 
larger ones are made up of 2, and sometimes of 3 or 4 fused nucleoli 
(figs. 84,86,88). Before the fusion of the nuclei is completed, how- 
ever, the number of the nucleoli begins to increase, until sometimes 
nearly 30 are present. These new nucleoli are apparently formed by 
simple budding of the large fusion nucleoli (figs. 92, 95). 
4. The endosperm and embryo. 
The egg, and likewise the whole contents of the embryo sac and 
seed, degenerate, as noted above, unless fertilization is accomplished. 
The occurrence of fertilization is indicated by the presence of two 
nuclei, of two nucleoli, or of a double-sized nucleolus in the egg and by 
the formation of the composite endosperm nucleus. The next evi- 
dence of further development in the sac, aside from the continued 
growth of all its parts, is the division of the endosperm nucleus. The 
first division of the egg itself does not usually occur until 8 or 10 en- 
dosperm cells have been formed. 
The primary endosperm nucleus, when the fusion of its 14 con- 
stituent nuclei is finally completed, is a rounded, though often some- 
what flattened and lobed structure. It is very large, having a diam- 
eter of 20 to 25 /X. It has a rather coarse and darkly staining, super- 
