( 509 ) 
Botany. — “Dipsacan and Dipsacotin, a new chromogen and a new 
colouring-matter of Dipsaceae’. By Miss T. Tamars. (Com- 
municated by Prof. J. W. Morr). 
If leaves of Dipsacus sylvestris are heated for a few hours in a 
moist -space to a temperature of 60° C., they acquire a fine dark- 
blue coloration. I have more closely investigated this phenomenon, 
which once accidentally came to my notice, and have studied the 
conditions of the formation of the blue colouring-matter dipsacotin, 
its properties and those of the chromogen dipsacan, the localisation 
of the latter and its distribution in the vegetable kingdom. At the 
same time I have traced the occurrence of dipsacase, the enzyme 
which splits the chromogen. 
Here I wish briefly to communicate the chief results of the in- 
vestigation; a more detailed paper on this subject will be published 
in Recueil des Trav. bot. Néerl. Vol. V, 1908. 
The investigation, which was chiefly carried out with radical 
leaves of Dipsacus sylvestris and fullonum, has shown that for the 
formation of the blue colouring-matter a temperature of at least 
35° C. and the presence of water and oxygen are necessary. 
Between 35° and 100° C. the rate of formation of dipsacotin in- 
creases with the temperature. It is only formed after the death of 
the leaf. No blue colouring-matter is formed in the living plant, 
even when exposed for several days to a temperature of 35°— 40° C. ; 
the pigment only appears in the dead leaves, when the plant is 
dying off. 
If leaves are dried very rapidly at a temperature above 30° C., 
no dipsacotin is formed, or only a very small quantity ; if, however, 
during the warming, the leaves are in a moist atmosphere,t hey are 
coloured blue. 
Neither does the blue coloration occur when oxygen is absent. 
Since it is extremely difficult to free the leaves completely from air, 
I have proved in another way, that oxygen is necessary. The 
chromogen can be extracted by warm water, and if the extract is 
warmed in a space completely shut off from the air, no dipsacotin 
is formed, even on heating for days together. As soon as the extract 
is warmed in contact with the air, the blue colour rapidly appears. 
The formation of dipsacus-blue is therefore accompanied by an 
oxidation. Experiments have shown, however, that the colouring- 
matter does not result directly from dipsacan by oxidation. An inter- 
mediate product is first formed, as is shown by the fact that the 
light yellow extract becomes yellowish red on being heated in a 
34 
Proceedings Royal Acad. Amsterdam Vol. XI. 
