210 J. MCA. KATER. 



MATERIAL AND METHODS. 



The root tips of growing Phaseolus seedlings were used. Since 

 a matter of considerable controversy was the subject of this work 

 it was thought desirable to use a number of fixatives. 



Flemming's strong gave excellent results, though only the 

 peripheral portion of the root could be used. Root tips treated 

 with this fixative show three degrees of fixation. In the outer 

 layers of cells the cytoplasm and nucleus appear quite normal, 

 though the linin of the nucleus is not quite so accentuated as in 

 Bouin's. The next few layers of cells appear to be poorly fixed, 

 but are valuable for comparison with the outer cells. The 

 innermost part of the root tip does not seem to have been 

 penetrated at all. 



Bouin's proved to be very valuable since it slightly swells the 

 chromatin and accentuates the linin. There w r as no indication 

 that the actual structure was hidden or changed, but rather that 

 certain features of normal structure were made more evident. 

 The cytoplasm was not as well fixed as in Flemming's strong. 

 The tissue was fixed all the way through. 



Alcoholic Bouin's and a mixture of three parts Bouin's to one 

 part one per cent, osmic acid gave only fair results, inferior in all 

 respects to Flemming's and Bouin's. Zenker's, Carney's and 

 corrosive-acetic-alcohol shrunk the cells to such an extent that 

 they were of no value whatever. 



Very slow dehydration was found to be essential. Starting 

 with thirty per cent, alcohol two to three days were consumed in 

 the process of dehydration. The tips were embedded in hard 

 paraffin and cut at 4 micra. 



The sections were stained in iron-alum-haematoxylin and 

 lightly counterstained with eosin. 



OBSERVATIONS. 



Since the principal object of this work is the interpretation of 

 the structure of the resting nucleus the logical starting point is 

 the reconstruction of daughter nuclei. This will be followed by 

 a description of the resting nucleus and the account will end with 

 the prophasr. 



Reconstruction oj Daughter Nuclei. One of the features prob- 

 ably responsible for the value of Phaseolus for a study of this 



