88 KANSAS UNIVERSITY SCIENCE BULLETIN. 



METHODS. 



The root-tips of Podophyllum peltatum are peculiarly fitted 

 for the study of mitosis in the vegetative cells of plants. The 

 cells are larger than those of the onion root-tip, and in properly 

 stained material the cell organs, especially the chromosomes, 

 are to be seen with almost diagrammatic clearness. 



The material used in this study was collected during the lat- 

 ter part of March and fixed in Flemming. For staining the 

 sections three methods were used: Haidenhain's iron-haema- 

 toxylin (some sections counterstained with orange G), the 

 safranin-gentian violet-orange G stain, and a combination of 

 these two. Satisfactory results were obtained with slides 

 stained in hsematoxylin, both with and without the counter- 

 stain; the three-color method also gave fair results. Only a 

 few sections were successful with the combination method, 

 but they were promising; without doubt the method will 

 repay careful experiment. It was followed as given by Schaff- 

 ner (2). 



THE RESTING CELL. 



The most typical resting cells are not often to be found at the 

 tip of the root, for this, of course, is the region of greatest 

 mitotic activity and the resting stages are very short, but back 

 from the tip as much as two millimeters. Farther from the 

 tip the cells are apt to be plasmolyzed in fixing. 



The nuclear membrane of the resting cell normally disap- 

 pears as soon as the cell begins division ; it is, however, quite 

 constant in its appearance and staining reaction, and varies 

 only slightly in thickness. It appears to stain very deeply with 

 chromatin stains, a fact which is probably due to the peripheral 

 arrangement of the chromatin granules, as seen in figure 1. 

 These chromatin masses are arranged over the linin network of 

 the nucleus in large or small patches, depending on the age of 

 the cell, i. e., nearness to the tip. 



In examining the achromatic structures of the cells of P. 

 peltatum I have had considerable difficulty, especially in the 

 stages of mitosis. In some cells they can be seen quite clearly ; 

 in others, which appear to be equally well fixed and have been 

 treated with exactly the same methods, they cannot be seen at 

 all. Owing to this irregularity in their staining capacity, I 

 have not been able to work out their history accurately. 



The nucleoli of these cells are yery interesting. They vary 



