No. 450.] 



STUDIES ON THE PLANT CELL. 



445 



conspicuous of the nuclear activities not only on account of the 

 position of the chromosomes (see Fig. 5), but because all kino- 

 . plasmic structures (the fibrillae and centrosomes or centrospheres, 

 if present) are shown to their best advantage. 



The best evidence indicates that the chromosomes of plants 





' - -^ ■ / H 



•'•s 



x:^ 



■' '?? 





Fig. 5. — Metapliases of Mito'sis. «, Saprolegnia; intranuclear spindle in oogonium, nucle- 

 olus outside of spindle. ^, Erysiphe ; mitosis in ascus, asters with rather small centro- 

 spheres. c, Corallina ; first mitosis in tetraspore mother-cell, very large and well 

 differentiated centrospheres. rf, Zamia ; blunt poled intranuclear spindle in central cell 

 of pollen grain ; blepharoplasts, their outer membrane about to break up. c, Pellia; first 

 mitosis in spore mother-cell; broad spindle with rounded poles, the very numerous spin- 

 ^dle fibers ending in granular kinoplasm. f. Agave; first and second mitoses in pollen 

 mother-cells ; (i), multipolar spindle just previous tn metaphase ; the several independent 

 cones of fibrillas gather more closely together to complete the spindle. (2) metaphase of 

 second mitoses; completed spindles showing however the several independent cones of 

 fibrillas. (After Harper, Webber and Osterhout.) 



only divide longitudinally. This matter has considerable theo- 

 retical interest, which will be considered in Section V, and also 

 in connection with the spore mother cell (Section III). The 

 daughter chromosomes are drawn apart by the contraction of the 

 fibrillae to which they are attached. 



Chromosomes may take on various forms during metaphase, 



