THK Sl'liKMATOGENESIS Ol IIVKKID PeAS 627 



The first division of the nucleus of the spore (/. J2) appears 

 to be similar to that of the somatic nuclei except for the number 

 of the chromosomes and the shape of the spindle. The chromo- 

 somes are of course the reduced number, and the spindle, owing 

 perhaps to the eccentric position of the nucleus, is somewhat trun- 

 cated. As in the two preceding divisions, the distribution of the 

 chromosomes in this one was apparently perfectly equable. There- 

 fore in all and in each of the nuclear divisions which were directly 

 connected with the development of the microspores the number of 

 the chromosomes, and also presumably the amount of chromatin, 

 were equally distributed. 



In late anaphase of the first division of the nucleus of the micro- 

 spore a cell-plate is seen separating the crescentic-shaped genera- 

 tive nucleus from the vegetative one. Reconstruction of the two 

 nuclei goes on at an unequal rate. The vegetative appears always 

 to form its wall in advance of the sister nucleus, and its chromo- 

 somes are also the first to become reticulated and lose their 

 identity. In the reconstruction of both nuclei excellent opportu- 

 nity was given to observe the beginning and extension of the nuclear 

 wall, which appear to occur precisely as Lawson has described.* 



Serpftte, Pure Race. 



The material of the pure parents of the Express x Serpette 

 hybrid at my disposal was not sufficient to permit an extended 

 study of either ; but some observations were made on the critical 

 stages of spore-formation in Serpette. 



The first maturation division in Serpette is heterotypic and the 

 second homotypic. In the anaphases of the first division the 

 chromosomes were not seen to be split, either for part or all of 

 their length, as was the case in the other pure races and the hy- 

 brids also. In the telophases of the daughter nuclei the chromo- 

 somes unite end to end and form a continuous daughter spireme. 

 In both maturation mitoses the reduced number of chromosomes 

 was seven. No differences in form or size were noticed between 

 the chromosomes of this and those of the other pure races. 



* Lawson, A. A. On the relationship of the nuclear membrane to the protoplast. 

 Bot. Gaz. 35 : 305. 1903. 



