THE REDUCTION DIVISION IN THE MICROSP0R0- 



CYTES OF AGAVE VIRGINICA* 



John H. Schaffner 



(with PLATES xh-xiv) 



This investigation, my fourth on the reduction karyokinesis, wis 

 undertaken to test the correctness of my former conclusions on a subject 

 apparently beset with many difficulties, judging from the numeroi 

 contradictory reports of various observers. Having obtained a 

 year's leave of absence from the university for travel and study, I 

 prepared suitable material of Agave virginka L., which was found very 

 favorable for my purpose. The stamens were collected and killed at 

 various hours of the day during the last week in June and the first in 

 July, 1907, a number of vigorous plants being in bloom on the cam- 

 pus of the Ohio State University. The killing fluid used was a weak 

 chrom-acetic acid solution (0.3 per cent, chromic and 0.7 per cent, 

 acetic in water). After imbedding in paraffin, the sections were cut 

 10-20 ji thick and stained on the slide. After experimenting with varioi 

 stains and combinations, Heidenhain's iron-hematoxylin was found 

 satisfactory, while Delafield's hematoxylin and the various safranin 

 combinations gave very poor results. This was probably due to the 

 readiness with which the cytoplasm took up and retained these stains 

 In the whole investigation great care was taken to have the section 

 correspond somewhat to the size of the nuclei, for sections too thick 

 or too thin may frequently give misleading figures. The nuclei in 

 the microsporocytes of Agave are comparatively small, 15-20 >* "J 

 diameter, so it was possible to obtain rather complete spirems and 

 spindles with rather thin sections. 



sre 



versity of Zurich, where the major part of the investigation was earned 

 on for his kindly assistance and courtesy shown me during my 09 

 1 n his laboratory. 



Contributions from the Botanical Laboratory of Ohio State University, XL* 



ical Gazette, vol. *,i f 1 ? 8 



Botanical 



