﻿240 BOTANICAL GAZETTE [april 



The eggs are formed during the process of nuclear degenera- 

 a tion described above, and their nuclear structure is really deter- 

 mined by that event. Trow (1899) has given a very good 

 account of the general stages in this process of protoplasmic 

 segmentation, but he did not know the cytological details, and 

 there is reason to believe that he may have been mistaken in his 

 interpretation of certain structures which he considered nuclei. 

 The first external indication of protoplasmic segmentation is the 

 gathering of the contents of the oogonium into denser masses 

 .around certain centers, these masses projecting into the central 

 vacuole and destroying that even outline present in earlier con- 

 ditions of the oogonium {^fig* 5). The protoplasm between the 

 ^oS" origins is less dense, and presently begins to develop small 

 vacuoles {Jig. 12), which run together until the egg origins are 

 separated by spaces of considerable size [/ig, ij). Many of 

 these vacuoles break through the films of protoplasm into the 

 central space, which then appears to have put out extensions 

 toward the celt wall. The protoplasm of the oogonium is excep- 

 tionally mobile at this time, and the vacuoles are constantly 

 changing their form and position. In the end the protoplasm 

 gathers more and more closely around the centers of the spore 

 origins, and finally the latter break away from one another at 

 all points of mutual contact [fig. ij), and the several independ- 

 ent protoplasmic masses round themselves off as eggs. 



The reader will have noticed in the illustrations of this proto- 

 plasmic segmentation that each egg origin has a deeply stained 

 > center surrounded by delicate rays [Jigs. 12-ij). These star-like 

 structures are very conspicuous under low magnification (in jf^^. 

 12 and IJ, 500 diameters) , when the center appears to be a single 

 structure. In reality it is not a simple unit, but is always com- 

 posed of at least two structures, a coenocentrum accompanied 

 by a nucleus. This dual nature is made clear only under high 

 magnification, with clear preparations of very thin sections. I 

 do not think it would be possible to understand the structure 

 from entire mounts such as Hartog's. Hartog probably consid- 

 ered the center as a nucleus alone, and certain of Trow's figures 

 indicate that he gave a similar interpretation. The coenocen- 



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