4 THE ROYAL SOCIETY OF CANADA 



blue is a complex of methylene blue and albumin-tannate. To 

 this view van Wisselingh (1914, p. 177), however, takes exception, 

 although perhaps it is not yet ascertained with certainty that the 

 precipitate is compounded of methylene blue and tannin alone. The 

 peculiarities of the precipitates observed by Loew (1906), both 

 himself and in collaboration with Bokorny, presented many micro- 

 chemical difficulties attributed by them to the presence of "labile 

 albumin." Similar difficulties are presented by the "aggregations" 

 caused in certain cells by ammonium carbonate, as first observed by 

 Charles Darwin (1882), and by the behaviour of the tannin in the 

 idioplasts in the cotyledons of Quercus (Lloyd, 1912). This difficulty 

 is exemplified further in some cases more recently examined by 

 myself, for example, in Eriogonum midtim, an herbaceous perennial 

 of the Pacific Coast, the more superficial cells of which contain 

 "tannin." If fresh material is placed in alcohol the tannin is extracted 

 in considerable amount. On sectioning, however, the tannin cells 

 are found to be unaffected so far as one can see — that is, they are 

 quite packed with what still appears to be tannin. On the application 

 of ammonium hydrate, however, the supposed tannin swells and 

 breaks away from its moorings (much as in Fig. 2, 4, PI, 2), while 

 the cell walls, which in life show no tannin reaction, do so after 

 treatment with alcohol. Here, then, the tannin appears to be both 

 extracted and left behind^ — an obvious absurdity. What really 

 obtains is, in my opinion, the following: Two substances are present 

 in the vacuole of the tannin cell, the tannin itself and another sub- 

 stance with the physical properties of a gel. In the case of the per- 

 simmon, this second substance has been shown by E. D. Clark (1913) 

 to be a "cellulose-like" substance which readily forms gelatinous 

 masses with water or alkaline solutions (I.e., p. 417) — thus confirming 

 my own earlier expressed opinion (Figs. 1-4, PI. 2). 



Again the behaviour of the tannin in the cortex and elsewhere 

 (the distribution of which has been described by Mell, 1911) of the 

 California tan-bark oak toward microchemical tests, is not that of 

 tannin as such alone. Bits of bark have been kept by me for several 

 years (since July, 1918) in alcohol. While the alcohol shows that 

 extraction of tannin has taken place the tannin cells are still as com- 

 pletely filled with material as before. This material still contains 

 tannin, but its insolubility in alcohol shows that it is not tannin 

 alone. 



The mode of occurrence of tannin is here somewhat similar to 

 that in the cotyledons of the oak, though not identical, I believe. 

 I have made a number of attempts to determine the exact nature of 



