416 The Physiology of Plants BOOK in 



darkness it is gradually decomposed with production of 

 amino-compounds. 



This labile protein, which is generally stored in the 

 vacuole, is sometimes met with in the cytoplasm also. It 

 can be shown by applying to the living cells certain dilute 

 solutions of organic bases or their salts, or of ammonia. 

 The best reagent is a 0-5 per cent, solution of caffeine or 

 antipyrin, which does not kill the protoplasm. The labile 

 protein separates in the form of little globules, which 

 gradually run together. Loew and Bokorny called these 

 proteosomes ; generally they contain traces of tannin or 

 lecithin. If the reagent is at once removed they dissolve 

 again. If the cells are killed, the droplets gradually change 

 their properties and become insoluble and solid. They 

 coagulate on heating. The reagents do not produce the 

 proteosomes in dead cells. Loew gave a fuller description 

 of the labile proteins and the proteosomes in 1899, but his 

 views were vigorously opposed by Pfeffer and his pupils, 

 who held that the proteosomes are compounds of ordinary 

 albumin with the caffeine. 



The latest speculations that come within our period were 

 those put forward by Verworn in 1894. They may be 

 stated here briefly, as they are much on the same lines 

 as the hypothesis of Pfliiger. According to Verworn there 

 are in the cell, beside the ordinary reserve store of proteins, 

 carbohydrates and fats, and the products of their decom- 

 position, certain other compounds also, probably protein 

 in nature, which change when the death of the cell occurs. 

 To substantiate this he relied on the facts of metabolism ; he 

 called attention to the instability of living and the relative 

 stability of dead material, the living being decomposed and 

 re-formed, giving off certain substances and taking in others. 

 Hence he argued that living substance must contain com- 

 plexes of atoms that have great tendency toward chemical 

 transformation and auto-decomposition, which may be called 



