358 MICROCHEMISTRY OF PLANT PRODUCTS 



creatin-glycerine ferments prepared by Dr. G. Griibler in Leip- 

 zig are solvents of proteids. Sections are treated for an hour 

 at a temperature of 40° C. with a mixture of i part of pepsin- 

 glycerine and 3 parts of water, to which is added 0.2 per cent, 

 chemically pure hydrochloric acid. Pancreatin-glycerine is 

 employed in the same manner as the pepsin-glycerine. 



Protein Crystalloids. — Under Aleurone in this chapter 

 are given methods for differentiating crystalloids in aleurone 

 grains. Protein crystalloids also occur in the cytoplasm, nucleus, 

 and chromatophores, and in all of these cases the crystalloids 

 have essentially the same nature, but they may vary considerably 

 in form. For staining crystalloids, see also in the last chapter 

 under Acid Fuchsin. 



Protoplasm. — The protoplasm of the cell can be studied to 

 advantage by means of the microscope only after being killed 

 and fixed by such reagents as those formulated under Fixatives 

 in the preceding chapter. The different constituents of the 

 protoplasm can then be differentiated by means of stains or 

 by means of digestive ferments, such as pepsin and pancreatin. 

 Iron haematoxylin, or a combination of fuchsin and iodine 

 green, or of safranin, gentian violet, and orange G, are specially 

 to be recommended for dififerentiating the different parts of the 

 protoplasm. For staining the leucoplasts and chromatophores 

 in general, see under Acid Fuchsin, page 302. 



Protoplasmic Connections.— The protoplasmic connections 

 between the plates of sieve tubes may be strongly stained by 

 acid fuchsin and aniline water (see page 302). More delicate 

 protoplasmic connections require the use of a swelling agent 

 for their demonstration. Sections of fresh material may be 

 fixed with a solution of 0.05 gm. of iodine and 0.2 gm. potassium 

 iodide in 15 gm. of water, and then the iodine should be replaced 

 by chloroidide of zinc, which should be allowed to act for about 

 12 hours. At the end of this time the membranes traversed by 

 the protoplasmic connections will be swollen to greater or less 

 extent, so that the chloroiodide of zinc may be washed out in 

 water and the sections stained by acid fuchsin and aniline water. 



