190 Darling: Sex in dioecious plants 



C. Eight chromosomes are formed by the segementation of 



■A 



the spireme thread. 



D. Five bivalent chromosomes come out of the nucleolus after 

 synapsis and after the spireme has become segmented into the other 



eight. 



E. There is no unequal distribution of the chromosomes in the 

 first division, and probably none in the second ; so that each pollen 

 spore contains thirteen chromosomes. 



F. In the reconstruction of the daughter nuclei after the first 

 division, each nucleus contains one large chromatin mass and 

 several smaller ones which lose their staining capacity as their 

 chromatin passes into the large mass. A secondary chromatin 

 mass appears in one of the two daughter nuclei ; this may or may 

 not fuse with the larger mass. 



G. In the formation of the chromosomes for the second divi- 

 sion, as nearly as can be determined, the same phenomena occur 

 as in the first division ; where two chromatin masses occur in one 

 of the daughter nuclei of the first division, the smaller mass, as well 

 as the large one, gives off chromatin in spherical bodies to build 

 up the chromosomes. 



H. In the reconstruction of the daughter nuclei after the second 

 division, the two derived from one nucleus contain each one more 

 chromatin mass than the two derived from the other. This differ- 

 ence in behavior of the chromatin in both the first and second 

 division seems to indicate a difference in the nature of the chromatic 

 substance in half of the nuclei. In the resting stage, all nuclei 

 have the same appearance, each with a single, spherical nucleolus 

 and several non-staining bodies around the nuclear wall. 



General conclusions 



The storage of the chromatin in the nucleolus and its later be- 

 havior in building up the thread, as noted In Acer Negiindo, does 

 not appear to be a phenomenon newly observed. Wager ('04) in 

 his work on the root-tip of Phaseolus, believes that the nucleolus 

 in the species studied contains nearly all of the chromatin ; and 

 that it is transferred previous to division Into the spireme thread, 

 which then segments into chromosomes. He reviews the litera- 

 ture upon the subject and comes to the general conclusion that in 



