306 
THE FUNCTION OF TANNIN. 
It will be seen from the foregoing abstracts that there is 
a radical divergence of opinion upon this point. Sachs, and 
with him Schroder,* * * § have observed no consumption of tannin 
in the plants investigated by them ; Dulkf found by quantita¬ 
tive analysis an increase of tannin in the autumn emptying 
of the leaves of the beech. On the other hand Wigand, 
Schell, and Tli. Hartig state explicitly that they have in many 
cases seen a decrease or consumption of tannin in the 
processes of growth. The point is one, therefore, of con¬ 
flicting evidence on a matter of considerable physiological 
importance. 
My investigations have been conducted upon the following 
lines :— 
1. To determine whether, as Wigand says, as the period 
of winter rest approaches, the quantity of tannin in stems 
diminishes pari-passu with the increase in the quantity of 
starch, so that the quantity of tannin is in winter at its 
minimum. 
2. Whether, as Wigand further declares, in spring the 
quantity of tannin increases as that of starch decreases; or, 
as Hartig asserts, in the oak there exists a “ Gerbmelil ” 
which is dissolved and used up in spring. 
3. Whether, as Schell believes, in germination and in 
stems in spring tannin is used up when the quantity of starch 
or other carbohydrate has reached a low point. 
Firstly, to take the contention of Hartig. 
In Quercus pedunculata, according to Hartig, \ the stems 
contain “ Gerbmehl.” Nageli§ had investigated this point, and 
found that Hartig’s Gerbmehl is starch saturated with tannin, 
and, hence, taking the iron reactions. lie tested it by satu¬ 
rating potato-starch with dilute solution of tannin, and found 
that the grains then gave the tannin reaction. Hartig, 
however, does not accept this explanation, for, as already 
noted, in 1878 he says that his opinion “ ist von Seite 
anderer Physiologen einer Priifung bis jetzt niclit unterzogen 
worden, und die von einer Seite erhobene Einwendung, dass 
das Gferbinelilkorn von fhissigen Gferbstoff durchdrungenes 
Starkemehl ‘ sem konne,’ eine durchaus willkiihrliche, gege- 
liitber dem von mir gefiihrten Nachweise, dass in den Gerbmehl 
* Schroder , Versuclisstat., 1871, Bd. 14, p. 118. 
f Bulk, ibid., 1875, Bd. 17, p. 192 ; see Pfeffer, Pflanzenpliys., I., 
p. 305. 
f Hartig. See also Anat. u. Pkys. der Holzpflanzen, Taf. I. 
§ Ndgcli. See Niigeli u. Sell wen dener, Das Mikroskop, 2 te Auflage, 
p. 492. 
