212 BOTANICAL GAZETTE [march 



PLATE XII 



Fig. i. — Microsporocyte showing resting chromatin network. 



Fig. 2. — Microsporocyte at a later stage showing masses of chromatin 



granules 



Fig. 2a. — A small portion of the chromatin net showing the linin and massing 



of the granules. 



Fig. 3. — A nucleus with prominent massing of the chromatin into rather 

 definite bodies, protochromosomes. 



Fig. 4. — Later stage; the chromatin masses stretching out into a definite 



spirem 



Fig. 5. — The delicate slender spirem complete. 



of the nuclear cavity. 



fig- 



the nuclear cavity is expanded . 



fig. 6; in fig. 



Fig. 11. — Nucleus with spirem becoming thicker 



Fig. na 



linin with a single row of chromatin granules 



fig. 11, showing the light-staining 



Figs. 12, 13. — Types of synizesis in a later stage than those of figs. 6-10. 

 Fig. 14.— Continuous spirem beginning to fall into loops, showing chromatin 



granules enlarged and partly double. 



Fig. 14a.— A short piece of 



of the chromatin granules. 



Fig. 15. — Same stage as fig 

 spirem. 



fig 



Fig. 16.— Beginning of the looped spirem, showing further thickening 



and 



doubling of the chromatin granules. 



Fig. 16a.— Pieces of tt 

 granules and distinct linin. 



fig 



loops. 



Fig. 17.— Continuous spirem, much thickened and thrown into 



twisted 



Fig. 17a.— Pieces of the spirem showing the method of looping and ***** 

 Fig. 18.— Microsporocyte somewhat later than fig. 17, showing further thic en 



«ng of the thread and development of the chromatin loops. 



Fig. i&i.— A number of chromatin loops before the breaking of the SP 1 *^ 

 Fig. 19 —Section of microsporocyte in which several loops can be fo 



out; the section represents nearly half of the spirem. . . to 



Fig. 20— Beginning of the broken skein stage; the chromosomes beginning 



break apart; three ring-chromosomes still connected. eakin g 



Figs. 20a, 206, 20c— Three complete chromosomes just after the brea 



of the spirem. 



Fig. 21.— Synizesis in microsporocyte at time of separation of chr ° m0S ^ em . 

 Fig. 22.— Nucleus with chromosomes completely separated; nuclear 

 brane still present. 



