CHAPTER XVII 

 MICROCHEMISTRY OF PLANT PRODUCTS 



Aconitine, CgjH^jNOij- — An alkaloid occurring in especial 

 abundance in the rootstocks of Aconitum Napellus. To demon- 

 strate aconitine treat sections with potassium iodide-iodine, 

 or with a solution of potassium permanganate. The first re- 

 agent produces a carmine-red coloration in the presence 

 of aconitine and the second gives a red precipitate of aconitin 

 permanganate. 



Aleurone. — See page i8i for a description of the nature 

 of aleurone grains. The protein nature of aleurone is dem- 

 onstrated by its dissolving with a red color in Millon's reagent 

 and by its being colored yellow or brown with iodine reagents. 

 Aleurone grains should be studied in a mixture of equal parts 

 of castor oil and 95 per cent, alcohol slightly colored with eosin. 

 In water they are in danger of going more or less into solution. 

 Permanent preparations of the aleurone of Ricinus may be made 

 by placing small bits of the endosperm in a saturated alcoholic 

 solution of picric acid, rinsing in alcohol, imbedding in parafi&n 

 (see page 261), sectioning on the microtome (see page 262), 

 staining in an alcoholic solution of eosin, rinsing in oil of cloves, 

 and then in xylene, and mounting in balsam- By this process 

 the ground substance should be red, the crystalloid yellow, and 

 the globoids colorless. For reaction of aleurone to other reagents 

 see in the last chapter under Borax-Carmine, Digestive Fluids, 

 Pepsin. 



Alkaloids. — Sections to be tested for alkaloids should be 

 thick enough to leave one cell layer intact. In order to make the 

 determination of the alkaloid more certain, sections for con- 

 trol should be soaked for a day or so in a solvent of alkaloids 

 prepared by dissolving i part of tartaric acid in 20 parts of alcohol, 



330 



