276 
THE FUNCTION OF TANNIN. 
resubstantiates liis earlier statements on the storage of tannin 
in the form of grains in the winter food reservoirs of plants 
(e.g., the oak), and its solution in the spring sap. He sums 
up his opinions thus:—“Die physiologisclie Bedeutung des 
Gerbmehls ist dieselbe wie die aller iibrigen Keservestoffe. 
Es wird in Frulijahrsafte der Baume aufgelost, olme seine 
Reaktion auf Eisensalzlosungen dadurch einzubiissen, im 
Sommer und Herbste jeden Falles in den zugewachsenen 
Baumtheilen neugebildet. Was und wie viel vom Gerb- 
mehlgehalt der Baume im Winter, auf Neubildung von 
Zellen im darauf folgenden Jahre verwendet wil’d, welclie 
veranderungen die Gerbmehlldsungen hierbei erleidet, ob der 
Gerbsauregehalt des Gerbmehles hierbei betheiligt ist, dafiir 
felilt mil* zur Zeit nocli eine lange Reihe nothwendiger Ermit- 
telungen.'’ (l.c. p. 123). 
So far for experimental evidence, and now for two opinions 
expressed upon the evidence afforded by others. 
De Bary* thus expresses himself on the subject:—“ It is 
true that the abundant presence of this body, tannin, in 
secretory sacs is not decisive, since it exists also elsewhere, 
in the epidermal cells, and in many, especially ligneous, 
plants, and particularly in the assimilating starch-forming 
parenchyma, and, as far as we know at present, it is at least 
undecided whether it exists here as a bye-product in con¬ 
structive metabolism, as is the case with calcium oxalate, or 
is a definite transition phase therein.” 
Sadist says:—“ Very widely distributed further are certain 
tannins, often mixed with a red colouring matter, and which 
are either present in special isolated cells, or in rows of cells, 
without being again used in metabolism, which therefore are 
to be considered as excreta. In other cases, on the other 
hand (e g., the germ shoot of the oak), there are tannins of 
another kind which, by their origin and disappearance and 
by their behaviour in growth, are to be recognised as special 
forms of reserve food-material, which find further use in 
metabolism . . . .” 
* De Bary, Vergleickenden Anatomie, p. 160. Some further 
references to literature will be found here, and also in Ndyeli u. 
Schivendener, l.c., and Pfeffer, Pflanzen-Pliysiologie, i., 305-6. 
f Sachs , Vorlesungen iiber Pflanzenphysiologie, 1882, p. 209. 
(To be continued.) 
