( 693 ) 
may even take place. Reserve-materials like starch and fatty oils 
may not be assumed to participate directly in the building of the 
cell wall. They must first be converted into soluble substances. Now 
suppose that tannins also belong to this category, i. e. to such a 
plastic material as is present in the plant in a dissolved state, then 
it is not at all surprising that for the maintenance of growth plenty 
of this material should always be present, and that occasionally, 
when more of it is being produced from the reserves than is used 
up in the growth of the cell-walls, the tannin content increases. 
Anyhow it has not been proved that, because the tannin does not 
diminish, it remains unused at the place, where it has been formed, 
and that it does not serve for the building up of cell walls. 
Like Sachs, Kraus 1 2 ) also assumes that an increase in the tannin 
content in germination proves, that this substance is not used up 
and does not serve as building material. Thus with regard to the 
germination of the acorn Kraus states, as a result of quantitative 
tannin determinations, that not only is tannin not used up, but that 
its quantity even increases, so that it *cannot be of service in growth. 
Whereas Sachs only observed an increase of the tannin content 
of germinating seeds, Schell 5 ) found in some plants an increase 
and in others a decrease or disappearance. In the first case Schell 
supposes, in agreement with Sachs, that the tannins are by-products 
of metabolism, but in the latter case he regards them as plastic 
material. With reference to what has already been said, it is a matter 
of course that I cannot either agree with Schell’s conclusions. In 
my opinion it is not necessary to conclude, on the ground of an 
observed increase in the tannin content in some cases and a decrease 
in others, that tannins behave so differently in different plants. 
Supposing the tannin to be a plastic material in both cases, then 
the occurrence of an increase or decrease will depend on the quan¬ 
tities produced and used up.' I also think it very plausible that in 
one and the same plant sometimes an increase, and sometimes a 
decrease takes place, according to circumstances. 
Several botanists suppose that tannins can undergo translocation 
in the plant. How this might happen is still a moot point, but there 
can be no doubt that the possibility of translocation greatly compli¬ 
cates the question of the use of tannins as plastic material. The 
increase or decrease of the tannin content of a particular organ would 
then not depend wholly on production and consumption, but transport 
1 ) Grundlinien, p. 38, 
2) l.c. p. 876. 
