292 BOTANICAL GAZETTE [april 



Degeneration may occur in any part of the gametophyte. Fre- 

 quently the second primary derivative degenerates before the first 

 ( n g- 37)- If sister primary cells are formed, the struggle resulting 

 from their parallel development is generally so great that disorgani- 

 zation of both results (fig. 32). Usually one gains the ascendency. 

 Often, after as many as three cells have been formed, one of the 

 antheridial groups is crowded against the wall; irregular cavities 

 appear in the cytoplasm (fig. 31); the protoplasm contracts and 

 accumulates in masses of globules; and the nuclei becomes massed 

 or uniformly granular (figs. 33, 53). When an extreme develop- 

 ment of the first antheridial cell occurs, the primary cell as well 

 as the secondary antheridial cell may disintegrate (fig. 33). 



Mitoses 



There are two types of mitoses; that characteristic of primary 

 divisions, and that of secondary divisions. The latter does not 

 differ essentially from ordinary somatic mitoses; the former is 

 quite distinctive in its characters. 



The nuclei and chromosomes are decidedly kinetic. Just 

 before mitosis, the primary nucleus moves to a more or less polar 

 position. Frequently it comes in contact with one of the primary 

 walls (figs. 14, 15, 16, 43). There is the usual movement of the 

 chromosomes to form the central plate at metaphase, and the 

 separation of chromosome groups during anaphase. After the 

 two nuclei have been formed, the one which is polar retains its 

 position, while the primary nucleus moves to its central or supra- 

 central position (figs. 5-7; 19-25; 43-45). 



The changes in the volume of the nuclear space are very marked. 

 During prophase a slight expansion is followed by a contraction 

 (figs. 14, 15, 16, 28) which continues until the disappearance of the 

 nuclear membrane. The chromosomes at the poles during early 

 telophase aggregate into compact masses (figs. 4, 18, 47, 49); the 

 nuclear membrane is formed, and the nucleus expands until it be- 

 comes three or four times its original size. There is an associated 

 accumulation or disappearance of food particles in the surrounding 

 protoplasm. This may be regarded as evidence in favor of Lawson's 

 (7) explanation of similar phenomena, namely, that they are due 



