THE FUNCTION OF TANNIN. 
275 
Wiesner* * * § believed that tannin is an intermediate member 
between the carbohydrates, starch cellulose, &c., and resin. 
Sachsse “ ist sogar geneigt, die Gerbsaure als eine Ueber- 
gangsbildung der Starke in Cellulose, anzunelimen, da diesen 
Uebergang immer unter Entwickelung von Koblensaure 
stattfindet. und von den Auftreten an Gerbstoffen begleitet 
ist.” t 
Hartig]; believed that tannin remained m the oak 
through the winter in the form of grains, very similar to 
starch grains. He called this “ Gerbmehl,” distinguished 
from starch by its solubility in cold water, and its reactions 
with iron. 
Schell,§ in the most extended researches into the distri¬ 
bution and function of tannin which have been published, 
arrives at the conclusion that in some cases tannin is a bve- 
«/ 
product of metabolism, in others an actual constructive 
material. He comes to this latter conclusion from its dis¬ 
appearance and subsequent reappearance during growth. In 
the germination of some oily seeds, e.g., Cynoglosswn vulgare, 
Anchusa officinalis , Asperity/) procumbens, Symphytum echinatum , 
Echium vulgare, the tannin begins to serve as a constructive 
material with the disappearance of the oil, and then 
diminishes in quantity; in all other cases, when the plant 
presents much oil or starch, and these do not disappear, the 
tannin is laid by as a bye-product. In the stem, amongst 
others, where it is present in some quantity during winter, it 
mainly disappears in spring. Schell believes in general that 
tannin acts as a constructive material only when the 
carbohydrates, oil and starch (? and sugar), are present in 
small quantities or are wanting ; the same occurring when 
plants [e.g., Eaba vulgaris) are germinated in unfavourable 
circumstances, as in pure sand. 
Tli. Hartig in his more recent publications || adheres to 
his old opinion on the nature and function of “ Gerbmehl,” 
* See Wiesner, Bot. Zeit., 1862, pp. 389-894, for further views on 
the relations between tannin and colours. 
t Sachsse , in “ Ebermayer’s Pliysiologisclie Cliemie der Pflauzen,” 
p. 412, is disposed to consider tannin to be a transition product from 
starch into cellulose, as this change always takes place with evolution 
of carbonic acid gas, and is accompanied by the appearance of tannin. 
I Hartig, “Ueber den Gerbstoff der Eiclie,” Stuttgart, 1869; see 
also Bot. Zeitung, 1865, pp. 53 and 237. 
§ Schell. I am acquainted with this paper only in the form of an 
abstract, “ Physiologische Rolle der Gerbsaure,” in Bot. Jahresbericlit, 
1875, pp. 872—8. The original is in Russian, 136 pp. quarto, with two 
plates, 1874. 
I) Hartig, Anatomie und Physiologie der Ilolzpflanzen, 1878, pp. 
119-123 ; “ I)as Gerbmehl.” 
