CHESTNUT BARK DISEASE. 405 
of the tree without the bark are used in the making of tannin 
extracts.” : 
W. M. Benson (54, p. 229) makes a statement regarding 
chestnut trees grown on different soils which, if true, possibly 
explains why, in very dry years, the trees suffer more from 
the blight than in wet ones, since there may be some relation 
between the amount of moisture and litne taken in by the roots 
and tannin produced in the tree. He says: “The chestnut 
wood received at the extract factories was at first supposed to 
be all alike in tannin strength, but costly experience proved 
that wood from good strong lime shale or limestone lands 
is far richer in tannin than wood from soils that are rocky, 
sterile, and contain little lime. The difference is so marked 
that even the workmen in the leach house at extract plants can 
tell when wood from a lime shale or limestone region is being 
leached simply by the unusual increase in the strength of the 
liquid obtained from such wood. Chemical analyses proved the 
same thing beyond all question, that in order for chestnut 
timber to attain its full tannin strength it must grow on lime- 
stone or lime shale soil.” 
The part that tannin plays in the economy of plants is not 
very definitely known. It has generally been supposed to be 
largely a waste product, which serves more or less as a pro- 
tective agent against animal and fungus attack. Some few 
writers have raised the question whether or not it might serve 
some use in the physiological activities of the plant, possibly in 
the way of food. 
For instance, Pfeffer (Physiol. of Plants, 1, p. 491-3) says: 
“Fungi can assimilate many aromatic bodies such as tannin, 
resorcin, hydroquinone, phloroglucin, etc., but except in the 
case of quinic acid most of these afford very poor food 
materials. * * * Tannins, phloroglucin, and apparently all 
aromatic substances which accumulate to any extent, are con- 
tained in solution in the cell sap, so that their presence does 
not injuriously affect the protoplast. * * * Tannins and 
glucosides are undoubtedly produced for definite purposes, 
and are not mere by-products produced under all circumstances. 
* * * In spite of numerous recent researches, but little is 
known as to the function of tannin.” 
26 
