8 The Plant World. 



slightly under-ripe fruits which * * * "first produce a 

 fine sweet taste, while it takes about half a minute for the taste 

 to detect any astringency; this of course being due to the fact 

 that the saliva, being a liquid of low osmotic strength, causes 

 in a few seconds a swelling and rupturing of the tannin-cells and 

 finally the development of astringency." The condition re- 

 ferred to is illustrated in his sixth figure, p. 573, (1906). The 

 formation of a whitish, granular substance on contact of the 

 "expelled cells contents" with water is noted, and this, it ap- 

 pears to be inferred, is due to the solution or disorganization of 

 the tannin-mass, although this is not stated exactly. 



In my own experiments I have found that the swelling of the 

 tannin-mass even to the extent illustrated in the figure above 

 quoted is not necessarily accompanied by a soluble condition of 

 the tannin. I have repeatedly isolated large quantities of tannin 

 cells from fruits which have been over-ripe for a week or even 

 longer and were so soft and waterv that the alcohol-insoluble 

 pectose * ran freely into a test-tube. Practically every cell 

 burst, and the tannin-mass extruded. Long standing in water 

 and in alcohol failed to show the extraction of even a trace of 

 its tannin, which, it should be added, could not be tasted in the 

 slightest degree. Furthermore, I have observed the same be- 

 havior in a few cells from a portion of fruit which had been ex- 

 posed to ethyl nitrite for several days, though most of them had 

 passed into a condition of dehydration from which they could 

 not be recalled to an extent sufficient to burst the confines of 

 the cell wall. (fig. 6). 



The swelling and extrusion in any event are together but 

 a stage in the progress of dehydration. Still later on the tannin- 

 mass will swell sufficiently to burst the cell wall, but, instead of 

 extruding, will simply tear open. The manner of this tearing is 

 quite characteristic, and suggests at once the appearance ob- 

 tained on tearing a stiff jelly or the coagulated white-of-egg.(figs. 

 3,5). 



It is, however, not easy to say precisely what the relation is 

 between the inhibition capacity of the tannin-mass and the in- 

 solubility of the tannin. t The tannin may be completely ex- 

 tracted from a hard fruit just previous to entering upon the 



♦Presumably. I have not investigated this as yet. 



JSince writing this I have succeeded in getting further light on this relation. The re- 

 sults will shortly be published. 



