144 BOTANICAL GAZETTE [august 



cytoplasmic. 



iheiy of the a 

 Nephrodium 



sperm 



meta 



chromosomes 



poles of the spindle. After telophase, 



cell contains a single blepharoplast. 



sperm mother 



When 



sperm mother cell, far apart from 



For the sake of convenience, we shall term this body, at present, the 

 Nehenkern. 



The blepharoplast in close contact with the nucleus increases 



n 



AMien the spindle becomes bipolar, the chromosomes at the 

 equatorial plate are arranged regularly, so that the counting of their 

 number is easily done from the polar view. These 64 or 66 bivalent ' 



chromosomes separate and two sets of daughter chromosomes, each 

 64 or 66, pass to the poles of the spindle, and daughter nuclei are 

 formed by the vacuolization of chromosomes. 



Granularization of cytoplasm now^ begins at the peripher}^ of the 

 equatorial plate and proceeds toward its center, and seems to replace 

 entirely the central spindles, so that the spore mother cell is divided 

 into ^wo hemispheres by the equatorial zone of granular cytoplasm. 



Except in the number of chromosomes, the second, the so-called 

 homotypic mitosis, is essentially the same in Nephrodium as the 

 typical mitosis of the vegetative cell; 64 or 66 chromosomes reappear 

 at the prophase of the second mitosis, split longitudinally, and are 

 distributed into spores. 



Spermatogenesis. — The mitoses in the vegetative cells of prothallia 

 are similar to those of the sporophyte. The number of chromosomes, 

 however, in this case is 66 or 64. The account of the mitoses which * 



take place from the cutting-off of an antheridial initial from the 

 superficial cell of the prothallia to the formation of sperm grand- 

 mother cells will be omitted. The number of chromosomes is always 

 66 or 64. 



I 



The sperm grandmother cell is characterized by the first appearance 

 of blepharoplasts. The blepharoplasts first appear as two small 



