SPECIAL METHODS. 2 1/ 



It is also always readily soluble in dilute caustic potash or 

 ammonia solution and in sodium phosphate. The last- 

 named reagent in concentrated aqueous solution is especially 

 recommended by Lu'dtke (I, 73). 



The fundamental mass of the protein granules behaves 

 very differently in different plants. In many, as in Pceonia, 

 it is soluble in water ; in others it is insoluble in it. It shows 

 similar relations with a 10$ solution of common salt and a 

 \% sodium carbonate solution, differing with the species of 

 plant. The protein grains which are soluble in water are 

 best examined in alcohol or glycerine ; and, by the gradual 

 addition of water, their solution may be observed under the 

 microscope. 



383. But the protein grains may be made insoluble by 

 fixing media, for instance by an alcoholic solution of corro- 

 sive sublimate or of picric acid. Objects fixed in the latter 

 fluid may be directly preserved in balsam. But it is also 

 -easy to stain the protein grains after washing out the fixing 

 fluid, and for this purpose an aqueous solution of eosin is 

 very useful. 



384. The fundamental mass of the protein grains is 

 bounded externally, as well as against the inclusions, by a 

 delicate pellicle which is distinguished from the remaining 

 substance of the protein grain by its insolubility in dilute 

 alkalies and acids, but, as has been shown by Pfeffer (I, 449), 

 also consists of albuminoid materials. According to Pfeffer, 

 it may be well observed by gradually dissolving the funda- 

 mental mass or the inclusions by the addition of very dilute 

 caustic potash, acetic acid, or hydrochloric acid. Liidtke 

 has lately recommended lime-water for the same purpose, 

 as it first dissolves the fundamental mass of the grain, while 

 the membrane becomes sharply visible and then dissolves 

 after a preliminary swelling. 



b. The Protein Crystalloids. 



385. The crystalloids observed in the protein grains of 

 many seeds consist always, like the fundamental mass, of 



