Nos. 4SI-45Z-] STUDIES ON THE PLANT CELL. 



579- 



which lie at a considerable distance from the structure (Fig. xob). 

 The latter cannot then be said to occupy the position of centro- 

 somes in relation to this spindle. Meanwhile important changes, 

 which are best known for Zamia, take place in the blepharoplast. 

 In this type the structure forms a hollow sphere which breaks 

 up into segments and finally into granules as mitosis proceeds.. 

 The radiations disappear without holding any apparent relation 

 to the spindle. During telophase each of the two blepharoplasts 



Fig. io. — Spermatogenesis in Cycas. a, Body cell in pollen tube with two blepharoplasts ; s, 

 stalk cell ; p, prothallial cell ; b, anaphase of mitosis in the body cell the spindle lying 

 between the two blepharoplasts which have begun to form cilia ; c, Blepharoplast elongat- 

 ing, in contact with a process from the nucleus; d, end of blepharoplast attached to the 

 nucleus at a later stage of development ; e^ sperm showing section of the flattened spiral 

 blepharoplast with cilia projecting beyond the cell. (After Ikeno, 'g8.) 



appears as a mass of granules at some distance from the daugh- 

 ter nuclei which are to become the sperm nuclei. As a result of 

 this division the spermatids (sperm mother-cells) are differen- 

 tiated. At the close of the mitosis the blepharoplast enters 

 upon its functions of formirfg in the spermatid a cilia bearing 

 band which is to lie as a spiral around the sperm. The granules 

 first extend as a delicate deeply stained line towards the nucleus 

 and then in the opposite direction. The nucleus in Cycas puts 

 forth a papilla (Fig. loc) which meets this line of granules and 

 remains attached to it for some time. The line thickens into a. 



