Nos. 451-452.] STUDIES ON THE PLANT CELL. 



There has been some discussion on the morphology of these 

 motile sperms of the gymnosperms. The claim has l)ccii made 

 that they are ciliated spermatids (sperm mothcr-cclls) and there- 

 fore different from the sperms of jitcritlopln tes wliit h are 

 formed inside of mother-cells that upon their csia])c are left 

 behind as empty cysts. However a close analysis of their struc- 

 ture will show that the sperms in both -roups ha\e an idc-ntical 

 protoplasmic organization. There is a nucleus and a .i;reater or 

 less amount of cytoplasm in which the blei)haroplast lies and the 

 entire structure is surrounded bv a plasma membrane. An\- 

 differences in the processes of spermatogenesis can only concern 

 the greater or less development of a cellulose membiaiie around 

 the spermatids. It may be true that this cellulose membrane 

 is entirely absent in Cycas and Zamia, but if present it would 

 be merely a shell like envelope around the s])erm and cannot 

 affect its morphological unity and agreement with the sperms 



of pteridophytes. A comparative study of the composition and 

 formation of the walls enclosing sperm nuclei in the sperma- 

 tophytes is much needed to carefully distinguish between plasma 

 membranes and the cellulose secretions that may be developed 

 by them. 



While the cycads and Ginko have very much the largest 

 sperms known and are consequently e.\tremel\- favorable for an 

 examination of spermatogenesis nevertheless some sur])risingly 

 detailed studies have been made among the Filicinea; and I^:(|uise- 

 tinccx. Following his preliminary announcements ('97a, '97b, 

 '97c), Belajeff published in '98 an account ot s|)ermatogenesis in 

 Gymnogramme and Equisetum. These torms present histories 

 parallel to each other and to the cycads. Two deeply staining 

 bodies (blepharopla.sts) api)ear on oj^posite sides of each nucleus 

 previous to the final mitosis in the antheridium which differen- 

 tiates the spermatids. Consequently each spermatid receives a 

 blepharoplast which lies close beside the nucleus. The bleph- 

 aroplast begins to elongate and is followed by the nucleus so 

 that both structures form two ])arallel bands which take a s])iral 



end of the sperm. The cilia of Equisetum could be traced to 



form. ^ (Illustrated 



The rest of the 



