﻿BOTANICAL GAZETTE 



[JANUARY 



A disk of rock salt M with plane parallel faces had holes bored 

 through it into which were inserted brass pins N, which served as 

 legs. In operation, these parts were placed in the tube, as shown 

 in the figure. The source of light was a hydrogen discharge tube, 

 as shown at 0. Its fluorite window was in contact with the fluorite 

 window D. 



In one method the apparatus was used as follows: The glass 

 stopper with its attached parts was removed from the tube, the 

 platinum hemisphere sterilized in a flame, and then placed convex 

 side upward upon the stage of a binocular dissecting microscope. 

 Fungus spores were transferred to the top of the hemisphere with a 

 platinum needle. By means of the binocular microscope the arrange- 

 ment of the spores on the platinum hemisphere could be easily 

 observed. After the spores were transferred to the dome a current 

 of air blown through sterile cotton was allowed to play upon the 

 hemisphere. All of the spores which were not in actual contact 

 with the platinum were thus removed. This treatment gave a thin 

 layer of spores quite evenly distributed over a small area at the 

 very top of the hemisphere. The platinum hemisphere was now 

 placed upon the platform H, and the screen M placed in position, 

 the glass stopper B inserted and carefully turned until an air- 

 tight joint was formed. The tube was then exhausted to about 

 o.ooi mm. mercury pressure, and the exposure made. After the 

 exposure, air was admitted into the tube and the stopper B 

 removed. The platinum hemisphere with the exposed spores was 

 again placed on the stage of the binocular microscope. A small drop 

 of agar had been allowed to solidify on the under side of the cover 

 slip of a van Tieghem cell. This cover slip was removed from the 

 cell and brought over the spores on the platinum hemisphere. Then, 

 while observation with the binocular microscope was being made, 

 the cover slip was carefully lowered until the " hanging drop " of agar 

 just touched the spores on the top of the hemisphere. The cover 

 slip was immediately lifted, taking the spores with it, and placed 

 back on the ring of the van Tieghem cell. The cell was then set 

 in an incubator. Because of the curved surface of the platinum 

 hemisphere the spores were transferred to the agar without chan- 

 ging their relative positions, and as the agar drop came in contact 



