406 CONNECTICUT EXPERIMENT STATION REPORT, 



Barnes (Textbook of Botany, i, p. 414) says concerning this 

 subject: "Some substances, including the loose term tannin, 

 are glucosides, and such as can be made to yield glucose by 

 digestion may be considered as plastic substances rather than 

 wastes." Stevens (Plant Anat, p. 205) also states: "Tannins 

 seem to be by-products, set aside in the tannin cells from the 

 general circulation. It is uncertain whether the tannins are 

 ever used to an appreciable extent in nutrition. They seem to 

 be of service, however, in warding off parasites by their aseptic 

 qualities and astringent taste." 



Cook (Delaware Agr. Exp. Sta. Bull. 91, p. 59), who studied 

 the effect of tannic acid on different species of fungi in 

 artificial cultures, says in his general summary: "It appears 

 that tannin is an important factor, and that its importance varies 

 in accordance with the other substances with which it is 

 associated in the cells of the host plant. While tannin no doubt 

 serves as a protective agent, its efficiency in this direction will 

 vary somewhat with the character of the other substances within 

 the cell. This may account for the variation in power of 

 resistance between species, varieties, and individual plants. The 

 fact that plants which produce large quantities of tannin are 

 subject to disease is no argument against the preceding. The 

 organism may live in tissues which bear little or no tannin, or 

 which contain other substances that in a measure counteract 

 the influence of the tannin. Furthermore, some species of fungi 

 are much more resistant to tannin than are others, and the species 

 which attack these high tannin-bearing plants no doubt possess 

 this quality." 



To the writer it has occurred that possibly tannin may serve 

 as an unusual source of food for certain trees rich in this 

 product under unfavorable conditions for active formation of 

 their normal food supply, such as drought years, and that such a 

 use would lessen the supply of tannin laid down in the annual 

 growth of wood formed in these years. Or possibly if not 

 used for food, these unusual conditions do not favor its normal 

 production. In any case, if tannin content bears a relation to 

 the blight disease, it is not the tannin of the whole tree that 

 counts so much as the tannin of the bark and wood of that 

 year's growth. If it bears any relation to the chemical activity 

 of the tree, we can readily see that it could easily vary from 



