bower) 
quantity, and especially in parts growing vigorously, it must indeed 
be an important substance to the plant. I imagine that dipsacan is 
continually formed and continually decomposed in the plant, and that 
the product of transformation, most probably that product which 
yields dipsacotin on oxidation, is used in various vital processes. 
In those places, where it is required, it is formed by the enzyme 
from the dipsacan present, and since it is not oxidized in the living 
plant to dipsacus-blue, we must conclude, that it is used up at once. 
Probably therefore dipsacan is the form under which the product 
used in metabolism, is stored up by the plant. This view not only 
explains the presence of the enzyme, but also the fact, that no 
dipsacus-blue is formed during life. 
Besides in Dipsacus sylvestris and fullonum, | have been able to 
demonstrate dipsacan in several other species of Dipsacus, and in 
various species of the genera Succisa, Scabiosa, Knautia, Astero- 
cephalus, Pterocephalus, Trichera and Cephalaria. It is not wanting 
in any of the members of the order Dipsaceae which I have examined, 
so that I conclude, that it is characteristic of this order. It does not 
occur in other plants, as was shown by an examination of about 
80 species, belonging to widely different orders. Only in the three 
species of the genus Scaevola of the order Goodeniaceae, which were 
at my disposal, I found, after warming parts of the plants in a moist 
space, that a blue colouring-matter occurs which is doubtless dipsacotin. 
The occurrence of dipsacan is therefore limited to two closely related 
natural orders, and a certain systematic value must undoubtedly be 
attached to it. 
Groningen, Botanical Laboratory, Nov. 23:d, 1908. 
Chemistry. — “On the bromation of toluol” and “On the sulfoni- 
sation of benzol sulfonic acid.’ By Prof. A. F. Hotieman 
and Dr. J. J. Porak. 
(These communications will not be published in this Proceedings). 
(January 27, 1909). 
