SOMATIC CHROMOSOMES IN VICIA 3ll 



simple physical fact that the removal of the stain is complète first in the 

 finer portions, the rétention being longer and longer as the structures be- 

 come coarser. One often observes in a single tapering strand that the color 

 grows gradually deeper in passing from the finer to the coarser part. It 

 seems that such an interprétation can be applied to many other accounts 

 describing chromatic granules upon a colorless Framework. 



From thèse considérations we must conclude that Vicia does not 

 afford good évidence for the existence of more than one substance in the 

 chromatic structures. If two substances are présent, for which certain 

 workers believe to hâve found évidence, one, the ground substance, is im- 

 pregnated by the other, the chromatic matter, in much the same manner 

 that the body of a chloroplast is said to be impregnated by chlorophyll. 

 Such an opinion is held by Grégoire and Wygaerts (o3), Grégoire (o6,) 

 LuNDEGARDH (oQ, lo, 12) and DiGBY (lo). BoNNEViE (o8, II) also believcs 

 two substances are thus combined, but holds that the achromatic material 

 is not contiuuous from one chromosome génération to the next. Her opinion 

 regarding the persistence of the chromosomes as spiral threads during 

 rest has already been mentioned. Frisendahl (12) finds in Myyicaria that 

 each of the very small chromosomes is represented throughout rest by four 

 (sometimes more) parts arising by a true split and further subdivision du- 

 ring telophase. Since the chromosomes of Vicia are relatively very large 

 we do not hâve a proper médium of comparison with Frisendahl's results. 



Prophase. 



The first indication that the prophasic changes hâve begun is seen in 

 the breaking down of the anastomoses along the Unes between the heavier 

 portions of the reticulum, so that each chromosome stands out as an irre- 

 gular reticulate and in places alveolar band connected with its neighbors 

 only by the finest anastomoses or not at ail, fig. 2. That thèse bands are 

 the same which went to make up the reticulum at the preceding telophase 

 seems highly probable from the fact that such bands are visible ail through 

 rest. Moreover, the anastomoses between the bands, being the most déli- 

 cate, would be the first to stretch out or break as the reticulum again gives 

 rise through condensation to the separate bands. The free ends of the 

 chromosomes are easily made out at this time, a point which must be 



40 



