( 686 ) 
again disappear from scientific terminology, but his suggestion did 
not receive any support. Waage 1 ) especially has objected to it. 
With reference to this question Dekker *) rightly remarks in his 
botanico-chemical monograph of the tannins, that there certainly 
exist plant substances, which are sharply marked off from other 
carbon compounds by common characteristic properties, such as the 
property of transforming animal skins into leather, which depends 
on the property of forming with protein compounds insoluble in J 
water, the adstringent taste, the presence of several phenolic hydroxyl- 
groups in the molecule, the power of precipitating alkaloids from 
aqueous solution and other properties; these substances must there¬ 
fore be collected in a separate group. Until the chemical constitution 
of these substances is completely known, the group in which they 
are united, should not be split up. 
Some authors, e. g. Reinitzer 3 ) and Braemer 4 ) consider that a 
group of plant substances cannot be studied physiologically so long 
as our chemical knowledge of it is incomplete. Waage 8 ), in my 
opinion, is quite right in not agreeing with this. Of course it will 4 
be necessary in the physiological investigation of tannins to ascertain 
in each case with the means at our disposal, whether the plant 
under investigation actually contains a substance belonging to the 
tannin class, so that confusion with other bodies may be excluded. 
The opinion of botanists concerning the physiological significance 
of tannins has always been much divided. Th. Hartig 8 ) supposed 
that tannins contribute to the building up of the vegetable organism. 
Schleiden 7 ) on the other hand considered that tannin is only a 
decomposition product of the ceil wall. 
In agreement with Hartig’s view tannin is, according to Wigand 8 ); 
a real factor in the chemical process of plant life and belongs phy¬ 
siologically to the group of carbohydrates, on the formation and 
transformation of which the life process of the plant is especially 
Eased. In co ntradistinction to starch, which appears as reserve ma- 
d ^ f W n“■'J? 1 * Beziehungen des Gerbstoffs zur Pflanzenchemie, Pliarm. 
Centralh. f. Deutschl. N°. 18, 1891, XII. Jahrg. N. F. p 247 
1. c. 1908, Vol. 1. p . V; Vol. II. p. 66; Vol. I. pp . 211 and 212. 
Bd^ p™' LCS tann ° Wes ’ 1890 ~ 91 * ^ Bot. Gentralbl. Jahrg. XII, 1891, 
6 )l.c. 
n Enlwickelun g s geachichte des Pflanzenkeims, 1858, p. 103. 
) M. ^ Schleiden, Grundzuge der wissenschaftlichen Botanik, 1861, p. 141. 
und der Pfl^nf^R ** ^ P h y siol °giscke Bedeutung des Gerbstoffes 
und der Pflanzenfarbe, Bot. Zeitung, 20. Jahrg. 1862, NO. 16, p . 121 and 129. 
