124 Allow Burdette Stout 



tened. They are often elongated in the direction of their alignment 

 in the spirem. 



Immediately after diakinesis the continuity of the bivalent discrete 

 spirem becomes still more conspicuous. At first it is variously twisted 

 about in the periphery of the nucleus (fig. 25). When two sister chromo- 

 somes lie in the plane of the section the paired condition is evident. When 

 this position is taken by several successive pairs the double spirem can 

 be traced without difficulty, especially if the pairs are rather close together. 

 The spirem is, of course, so twisted that in the sections one of a pair of 

 chromosomes frequently lies below the other and then the pair, except 

 on careful focussing, may appear as one mass. 



The important fact that can be established in Carex is that follow- 

 ing the post-synaptic spirem the chromosomes reappear as oval bodies 

 exactly comparable in size, shape, and number with those of the somatic 

 prophases in the root tip and that these chromosomes here also have 

 a definite serial arrangement. The only difference between this spirem 

 and the vegetative spirem is that here the serially arranged units are 

 double. 



Early in diakinesis cytoplasmic changes preparatory to the forma- 

 tion of the heterotypic spindle may be seen. At first there is an accu- 

 mulation of semi-fibrillar material about the nucleus. From this there 

 develops a felted zone of rather short fibres which gradually become 

 more conspicuous and form a weakly developed multipolar spindle. The 

 multipolar stage is, however, not sharply marked and soon changes to a 

 broad-poled spindle precisely like that of the somatic divisions. 



The spindle fibres in all divisions stain readily and the entire spindle 

 figure is conspicuous. While all stages of the early development of the 

 spindle outside of the nucleus can be easily traced, I have not observed 

 any definite intra-nuclear fibres such as have been noted in certain flower- 

 ing plants especially by Allen (1903 and 1905) for Larix and Lilium. 

 I find no evidence as to the nature of the intra-nuclear mechanism which 

 operates previous to the breaking down of the nuclear membrane. In the 

 prophases of the somatic divisions the chromosomes draw away from the 

 membrane, the spirem becomes centrally aggregated and then loosens 

 somewhat before the nuclear membrane breaks down and the visible 

 spindle fibres grow into the nuclear cavity. In the heterotypic prophases 

 still more complicated processes occur. After diakinesis, however, the 

 double spirem behaves similarly to the single spirem of somatic divisions. 



It is noticeable that in all resting nuclei the chromosomes are de- 

 cidedly peripheral. They lie against the nuclear membrane. In the 



