TANNIN AND ALLIED SUBSTANCES. 361 



The oils form very intimate mixtures with the albuminoids in 

 many cases, especially in seeds of such plants as Eieinus, etc. 

 According to Sachs, *•' in the germination of all oih' seeds, sugar 

 and starch are produced in the parenchyma of every growing 

 part, disappearing from them only when the growth of the masses 

 of tissue concerned has been completed. Since, in the case of 

 Eieinus, the endosperm grows also independently, starch and 

 sugar are, in accordance with the general rule, temporarily pro- 

 duced in it. The cotyledons apparent!}' absorb the oil as such 

 out of the endosperm, whence it is distributed into the paren- 

 chyma of the hj-pocot^'ledonary stem and of the root, serving 

 in the growing tissues as material for the formation of starch and 

 sugar, which on their part are only precursors in the production 

 of cellulose. In these processes tannin is also formed, which is 

 of no further use, but remains in isolated cells, where it collects 

 apparently unchanged until germination is completed. It can 

 scarcely be doubted that the material for the formation of this 

 tannin is also derived from the endosperm, although perhaps only 

 after a series of metamorphoses. The absorption of oxygen, 

 which is an essential accompaniment of everj' process of growth 

 and especially of germination, has in this case, as in that of all 

 oih' seeds, an additional significance, inasmuch as the formation 

 of carbohydrates at the expense of the oil involves the appro- 

 priation of oxygen." ' 



Vegetable wax is closely allied to the fats. 



953. Products free from nitrogen. IV. Certain astringents. 

 This indefinite group comprises various matters differing slightly 

 from one another in some particulars, but agreeing in possessing 

 a faint acid character, in changing color with salts of iron, and 

 in combining with certain protein matters. Tannin is sometimes 

 placed in the next category, namelj', among the glucosides ; but 

 according to Schiff it is digallic acid. The most important mem- 

 bers of this group are Ihnnin (the so-called tannic acid), Gallic 

 acid, and the astringent principle in Cinchona, Catechu, and 

 Kino. According to Niigeli, these matters are to be found in 

 buds, in unripe fruits, and in those petals which become red or 

 blue, dissolved in the cell-sap and diffusing through cell-walls. 

 Tannin sometimes exists in little globules of solution, enveloped 

 bj' a delicate film of albuminous matter ; for example, in the cells 

 of the pulvinus of Mimosa and in the bark of many ligneous 

 plants (Birch, Poplar, etc.). The following views are held as to 



1 Text-book, 2d English ed., p. 716. 



