50 ANATOMY AND PHYSIOLOGY 



concerning the occurrence and distribution of carbo- 

 hydrates in plants. 

 C. Tests for Cellulose: 



1. Mount a few threads of cotton (cotton wool) in 

 water under a cover glass. Cotton fibers are com- 

 posed largely of cellulose. Irrigate under the cover 

 glass with a little dilute sulphuric acid, and follow 

 the acid with the iodine solution. Draw the various 

 liquids under and away from the cover glass with 

 a small piece of blotter or filter paper. Observe 

 changes throughout under the microscope. 



Observe and record the color of the cotton fibers 

 after treatment with iodine. 



2. In a similar manner observe the color change when 

 freshly mounted cotton fibers are irrigated with a 



, solution of Chlor-iodide of zinc. 



3. Mount thin sections of various portions of plant 

 tissue, such as herbaceous stems, or bits of leaf epi- 

 dermis, a few threads of Spirogyra, or plant hairs 

 such as are readily obtained from leaves of mullein or 

 squash, and apply the above tests. Of what sub- 

 stance are the un transformed cell- walls of plants 

 composed? 



