6O MICRO-CHEMICAL REAGENTS. 



the various substances which are found in the 

 tissues or cells for the mixed colors. 



Protoplasm is stained violet-blue. Amyloid sub- 

 stances, the nucleus and gums assume various 

 shades of red ; the membrane of the nucleus stains 

 bluish ; resins, pure blue (the cuticle also colors 

 blue in many colleters). Tannin assumes a foxy 

 color; the cell -wall stains pale violet, deeper if 

 it contains lignin, reddish if it is more gelatinous. 

 Bast cells are stained a deep red ; sieve tubes and 

 the soft bast do not assume any intense color, 

 which is of advantage in the study of the fibro- 

 vascular bundles of endogens. 



METHYL VIOLET 



Has been recommended as a staining agent for 

 bacteria by Koch, 1 whose methods we give. 



A few drops of a concentrated tincture of me- 

 thyl violet are added to 15 to 20 gm. of distilled 

 water, so that this is deeply colored. With a 

 small pipette a couple of drops of this are placed 

 upon the film of bacteria to be colored, where the 

 fluid is allowed to flow back and forth until it is 

 thought that the specimen is sufficiently stained. 

 After a little practice it is easy to determine the 

 proper concentration for the fluid, and the length 

 of time it requires to act. If it is too weak the 

 bacterian film loosens from the glass, while if it 



1 Koch : Cohn's Beitr. z. Biol. der Pfl., II., p. 406. 



