﻿64 Hance : Pollen development in Zebrina pendula 



It gives me great pleasure to gratefully acknowledge the many 

 valuable suggestions offered by Professor H. M. Benedict during 

 the progress of my work. 



Material and Methods 



The cultivated wandering Jew was selected because of the 

 ease with which it can be raised in the house and because it 

 flowers steadily through the winter months. 



Weak and strong Flemming's solution, equal parts of glacial 

 acetic and absolute alcohol, and Gilson's killing agents were used 

 and the strong solution of Flemming was found to be by far the 

 most satisfactory. The material remained in the fixing fluid from 

 six to twelve hours, and was washed in running water for a similar 

 length of time. 



As Zebrina pendula produces at various intervals from eight to 

 twelve or more flowers at one point numerous stages may be found 

 in a single piece of material. 



Iron alum haematoxylin proved excellent but by far the best 

 results were obtained with safranin counterstained with light 

 green. The chromosomes are very large and when stained with 

 safranin stand out with a sharpness that makes counting and 

 drawing simple. The slides were allowed to remain from two and 

 one half to three hours in safranin and from two to three seconds 

 in light green followed by absolute alcohol, clove oil fifteen min- 

 utes, xylol three to four minutes and mounted in balsam or euparal. 

 The latter was found to be excellent for the quickness with which 

 it hardened and the clearness of the finished slide. Sections were 

 cut lo n thick though 15 or 20 ^ would be better owing to the size 

 of the cells. 



Most of the figures were drawn from the safranin preparations. 



Development and Degeneration of the Pollen 

 Heterotypic Division 

 Prophase. — ^The earliest stage observed is pictured in FiG. i. 

 The nucleus is composed of a dense network and two nucleoli 

 stand out sharply. One is larger than the other and each is 

 surrounded by a clear area. The growth period that ensues is 

 figured in the next few drawings. In Figs. 2 and 3 the cytoplasm 

 has apparently grown away from the nucleus. This may be an 



