I-j YEAST. 7 



A. Morphology. 



1. Spread a little out, on a slide, in a drop of the fluid, 

 and examine it "with a low power (-| inch objective) 

 without a cover-glass. Note the varying size of the 

 cells, and their union into groups. 



2. Cover a similar specimen with a thin glass and exa- 

 mine it under a high power (^ or better J objective. 

 Hartnack, No. 7 or 8, Oc. 3 or 4). 



a. Note the size (measure), shape, surface and mode 

 of union of the cells. 



b. Their structure : sac, protoplasm, vacuole. 

 a. Sac; homogeneous, transparent. 



/3. Protoplasm; less transparent ; often with a few 

 clear shining dots in it. 



7. Vacuole ; sometimes absent ; size, position. 



8. The relative proportion of sac, protoplasm, and 

 vacuole in various cells. 



Draw a few cells carefully to scale. 



3. Eun in magenta solution under the cover-glass. (This 

 is readily done by placing a drop of magenta solution 

 in contact with one side of the cover-glass, and a 

 small strip of blotting paper at the opposite side.) 



a. Note what cells stain soonest and most deeply, 

 and what part of each cell it is that stains : the sac is 

 unaffected ; the protoplasm stained ; the vacuole un- 

 stained, though it frequently appears pinkish, being 

 seen through a coloured layer of protoplasm. 



4. Burst the stained cells by placing a few folds of blotting 

 paper on the surface of the cover-glass and pressing 

 smartly with the handle of a mounted needle : note 

 the torn empty and colourless, but solid and un- 



