276 Plant Physiology 



Test the solubility of cellulose (cotton fibers) in concentrated 

 sulfuric acid and in cuprammonia. In the first case use small 

 quantities of the materials, rub up in a Syracuse watch glass, 

 when dissolved neutralize with KOH and test for reducing sugar 

 (glucose). 



With half-concentrated sulfuric acid determine the length of 

 treatment required to yield a blue color with iodine. 



Place cotton fibers, sections of a root-tip, etc., in a solution of 

 chloriodide of zinc (dissolve chloriodide of zinc in less than its 

 weight of water and add metallic iodine until a bright cherry 

 color is produced). Place the material in the concentrated solu- 

 tion, examine under the microscope, and describe the character- 

 istic color reaction. 



Fats and oils. - - The fats and oils are generally soluble in 

 ether, chloroform, benzene, and other solvents of this nature, 

 and certain oils (castor oil) in absolute alcohol. Examine 

 sections of the endosperm of castor-bean and of the garden bean 

 in water ; then after immersion for a few minutes in absolute 

 alcohol and ether, reexamine. Stain similar sections from a few 

 minutes to hah 3 an hour with a 50 per cent alcoholic solution of 

 cyanin (or in a solution of alcanna in absolute alcohol, then 

 diluted to 50 per cent) and note the deep color of the oily bodies. 



Proteins. - - Proteins may be soluble in water, in salt solutions, 

 in alcohol, and in acids and alkalies. Make sections, or shave 

 off with the razor fragments from the endosperm of wheat, 

 mount in water and examine for "aleurone " grains (not soluble 

 in water) in the outer layer particularly. In the same way 

 examine sections of the endosperm of castor-bean for protein 

 crystalloids and globoids, preferably after removing the oil (in 

 this case) by immersion for a few minutes in absolute alcohol. 



Mix some wheat flour and water, place in a cloth bag and 

 knead under a stream of water at the faucet. The glutinous 

 dough resulting after the starch is washed out is the gluten of 

 wheat, consisting of a mixture of protein substances some of 

 which, in the living cells, are indistinguishable from the cyto- 

 plasm. Take a small portion of this gluten, rub it up with a 

 2 per cent salt solution, and save for later study. Test the sol- 



