I.] 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 (J 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 (J or better 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. 



ft. Protoplasm; less transparent; often with a few 



clear shining dots in it. 



7. Vacuole / sometimes absent ; size, position. 

 & The relative proportion of sac, protoplasm, and 



vacuole in various cells. 

 Draw a few cells carefully to scale. 



3. Run 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- 



