160 BOTANICAL GAZETTE [march 



thickness (fig. 56). Then the same process occurs as was described 

 in vegetative mitosis. On account of the large number of chromo- 

 somes, the best stage for an accurate counting is obtained in the late 

 anaphase, in which two sets of daughter chromosomes are regularly 

 arranged near the poles (fig. 57). The polar view of this stage showed 

 128 or 132, or in rare cases 130, chromosomes (fig. 58). 



Mitoses that occur following this first segmentation division, during 

 the development of the embryo, were traced up to the appearance of 

 the first leaf. The process is essentially similar, and 128 or 132 

 chromosomes are invariably present. 



Discussion of cytological phenomena 



The origin of the blepharoplast. — There have been many contribu- 

 tions concerning the origin and structure of the blepharoplast, not only 

 in sperms of gymnosperms and pteridophytes, but also in zoospores of 

 thallophytes. 



In Cycas (Ikeno 41, 42, 43, 48), Ginkgo (Hirase 36, 37, 48), 

 and Zamia (Webber 94, 95, 96), two blepharoplasts first are formed 

 de novo in the cytoplasm of the body cell at some distance from the 

 nucleus, and one of these blepharoplasts is included in each sperma- 

 tid ; accordingly the origin of the blepharoplast is cytoplasmic. 



In Equisetum and Gymnogramme, Belajeff (6) observed the 

 blepharoplasts as two deeply stained bodies on opposite sides of the 

 nucleus previous to the final mitosis which differentiates the spermatid. 

 In Marsilia Shaw (80) discovered two blepharoplastoids in the telo- 

 phase of the mitosis which differentiates the grandmother cell of the 

 spermatid. The blepharoplastoids disappear in the spermatid grand- 

 mother cell, in which two new blepharoplasts are formed at the poles of 

 the spindle. Belajeff (7) examined the same form which Shaw had 

 studied, and he found two centrosome-like bodies at the poles of the 

 spindle of the mitosis which gives rise to the spermatid grandmother 

 cell. These centrosome-like bodies are probably structures similar to 

 the blepharoplastoids of Shaw; however, according to Belajeff's 

 accounts, these structures do not pass into the cytoplasm to disappear, 

 but accompany each daughter nucleus in the telophase and in the 

 prophase of the next mitosis which occurs in the spermatid grand- 

 mother cell. This centrosome-like body divides and the two resulting 



