266 • BOTANICAL GAZETTE [march 



are present at only one or more than one spermatogenous mitosis. 

 So far as actual evidence goes, it is possible to state unreservedly 



from 



i 



single mitosis 



form the usual functions of centrosomes. The discovery of frag- 

 mentation in the blepharoplast of a bryophyte serves to confirm 

 the view that the blepharoplasts of all groups above the algae are 

 homologous structures, and the details of the process aid mate- 

 rially in accounting for the behavior of those blepharoplasts which 

 have become least centrosome-like. 



Summary 



i. Centrosomes are present in Blasia at all stages of the mito- 

 sis which differentiates the androcytes, and in the androcytes they 

 persist and function as the blepharoplasts. 



2. In the transformation of the androcyte into the spermato- 

 zoid, the blepharoplast fragments repeatedly by simple fission, 

 forming a number of distinct granules which coalesce to form a 

 short lumpy rod. This rod elongates and becomes a more uniform 

 thread bearing two cilia, while the nucleus also elongates in inti- 

 mate union with it to form the body of the spermatozoid. The 

 present instance is the first in which blepharoplast fragmentation 

 has been reported in a bryophyte. 



3. It is possible that the fission of the Blasia blepharoplast, and 

 therefore the more complex fragmentation of the blepharoplasts 

 of Equisetum, Marsilia, and the cycads, may be homologized with 

 the normal division exhibited by ordinary centrosomes. 



Cornell University 



LITERATURE CITED 



1. Allen, C. E., Cell structure, growth, and division in the antheridia of 

 Polytrichum juniperinum Willd. Archiv Zellforschung 8:121-188. pis. 



6-g. 1912. 



2. , The spermatogenesis « 



31:269-292. pis. 15, 16. 1917. 



Ann. Botany 



orphology 



Ann. 



Botany 27:511-532. pis. 37,38- 1913. 



