230 THE AMERICAN NATURALIST. [VOL. XXXIX. 



The same principles have been established in plants by recent 

 investigations, some ot which deal with oogenesis and spermato- 

 genesis and will be specially treated in the Section V while others 

 treat of the behavior of the chromosomes when the gamete nuclei 

 fuse and the sporophyte generation begins its development. The 

 latter conditions concern the present discussion. 



The history of the chromosomes in plants at the time when 

 the gamete nuclei fuse (fertilization) is most accurately known 

 for the pine. The last paper upon this type (Ferguson, : 04) is 

 very complete. Miss Ferguson gives a beautiful series of figures, 

 some of which we have reproduced. The sperm nucleus comes 

 in contact with the egg nucleus and sinks into the latter so that 

 it lies in a depression, but as noted by Blackman ('98), it does 

 not penetrate the membrane of the egg nucleus (Fig. 17, a). 

 Both gamete nuclei thus lie side by side occupying approxi- 

 mately the same space formerly filled by the female. Each 

 shortly gives evidence of preparation for the mitosis following 

 fertilization (first cleavage spindle). The chromatin of the egg 

 nucleus collects in a spirem, very close to the sperm, occupying 

 a relatively small portion of this large female nucleus (Fig. 17, b). 

 The chromatin of the sperm nucleus also takes position as a 

 spirem on the side nearest its companion chromatin of the oppo- 

 site sex. The remaining space of each nucleus is filled with a 

 granular reticulum of a linin nature. At this time the amount 

 of linin is extraordinarily large in proportion to the chromatin, 

 suggesting that some of the latter substance has become changed 

 to the former. Soon, delicate fibrillae appear around the two 

 spirems growing outward in various directions and finally cross- 

 ing from one nucleus to the other. At the same time the two 

 nuclear membranes become less distinct and shortly disappear. 

 Thus the maternal and paternal spirems come to lie in a com- 

 mon area filled with delicate fibrillae which run out to the gran- 

 ular cytoplasm that lay around the two gamete nuclei (Fig. 17, c). 

 It should be especially noted that at no time in this history has 

 there been a resting nucleus including both maternal and pater- 

 nal chromosomes within a common nuclear membrane. The 

 fusion of the gamete nuclei has only come with the actual 

 formation of the first cleavage spindle. 



