NUTRIENT MEDIA AND METHODS OF CULTIVATION. 125 



commonly used for accurate observations, such as Sohafer's or 

 Strieker's, owing to their interference with the ilhimination. To 



Fig. 53.— Section of Iskael's Warming Appahatuk and Dkop-cultuee 



Slide. 



overcome this an apparatus has been constructed by wdiich the 

 sHde is warmed from above (Figs. 52, 53). 



The drop-culture sHdes are provided with a shallow groove, -1 mm. 

 deep and 1 mm. broad, cut round the concavity. Into this the 

 cover-glass fits, so that its upper .surface is level with that of 



Fig. 54.— Ishael's War.ming Apparatus. 



the slide. The heating apparatus consists of a flat disk-shaped box 

 with a central conical aperture. 



The entrance and exit pipes are fixed on at a right angle to the 



