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 lime 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, i, 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 



