1883.] of Tannins in the vegetable cell. 393 



the sensitiveness of the organ in question. Thus in Robinia pseu- 

 dacacia the movements executed by the main pulvinus are but 

 few when compared with those of the pulvini of the leaflets, and 

 one finds that the amount of tannin in the secondary pulvini 

 greatly exceeds in proportion that present in the main pulvinus 

 of the leaf. 



Again, in the development of galls there is at first no tannin 

 present, the gall tissue being simply a luxuriant growth in conse- 

 quence of the stimulation produced by the presence of foreign 

 bodies, viz. the egg and a small quantity of liquid — probably formic 

 acid — injected by the insect into the tissue. Later on, owing to 

 the irritation produced by the grub and the consequent stimulation 

 of the protoplasm, tannin is formed in the cells and, as in the case 

 of the spangle-gall, a quantity of starch also. Lastly, Schimper's 

 researches on Sarracenia and Utricularia, in which he has shown 

 that the gland cells are peculiarly rich in tannin ; are of great 

 value, since there again the protoplasm is extremely irritable and 

 will respond to stimuli. All these facts appear to point to one and 

 the same conclusion; that tannin is produced as a result of active 

 metabolism, consequent either upon the rapid production of cells, 

 as in the growing point, or consequent upon direct stimulation, as 

 in pathological or irritable tissue. 



As to the formation of tannin in the cell, it has been noticed 

 that it usually occurs simultaneously with starch, and it has been put 

 forward that starch goes to form tannin. At present however we 

 have no evidence that this occurs. As Miiller 1 pointed out, the 

 simultaneous presence of starch and tannin in a cell does not prove 

 that the latter is derived from the former, and our chemical evi- 

 dence suggests that this is not the case. It is possible that the 

 glucose part of tannin is formed from starch, but as far as regards 

 tannic acid, it seems much more reasonable to suppose that it is 

 formed directly from the protoplasm. 



Finally, we have to consider the fate of tannin. The balance of 

 evidence is certainly in favour of the view that tannin is a waste 

 product and, as such, of no further use to the plant. In support of 

 this view we have the fact of the occurrence of such large quanti- 

 ties of tannin in those parts of the plant which are thrown off, such 

 as the leaves and the bark. In growing points tannin appears to 

 be present in all the cells of the tissue 2 , but it gradually becomes 

 stored up in certain definite cells which are either isolated or in 

 rows. In this respect it l'esembles such waste products as calcium 

 oxalate. In a cutting of Cerasus lauro-cerasus, where the root had 

 been formed and a quantity of shoots were being produced, I found 

 that in the old leaves, which must have carried on the greater part 



1 Miiller, Pringsheim's JalirbiicJter, v. 1806. 

 - Kutscher, loc. cit. 



