693 
Botany. -— “On the demonstration of carotinoids in plants. Third 
communication: Zhe leaf of Urtica dioica L., the flower of 
Dendrobium thyrsiflorum Rehb. fil. and Haematococcus phiviales 
Flot” Prof. By C. van WrsseriNGm. (Communicated by Prof. 
J. W. Motu), 
(Communicated in the meeting of October 26, 1912). 
In the first and second communications I have shown that carotinoids 
in plants present differences in the colour and shape of the crystals 
and in their behaviour towards reagents and solvents. It is obvious 
that the presence of different chemical bodies cannot be assumed 
when the crystals only differ in colour and shape or when only a 
slight difference can be observed on the addition of a reagent or 
a solvent. When, however, important differences in colour and shape 
accompany a very remarkable difference of behaviour towards reagents 
and solvents, then such a conclusion may be justified. I will show 
by means of a few striking examples that the latter case applies to 
the carotinoids found in plants. 
Leaf of Urtica dioica L. 
The substances accompanying the chlorophyll of the stinging-nettle 
have been accurately investigated chemically. We know from the 
investigations of Wirrsrärrer and Miwa) that two carotinoids are 
present in the leaves of the stinging-nettle, carotin identical with 
Daucus-carotin, and xanthophyll. These chemists found four times 
as much xanthophyll as carotin. 
When leaves of Urtica dioica or leaf fragments are placed in 
Moriscn’s reagent and examined after a few days, there is found in 
each cell containing-chlorophyll an aggregate of red crystals resembling 
small parallelograms or needles and of orange-yellow plates, which 
are several times more long than broad and show more or less rounded 
ends; sometimes a few orange-yellow curved filamentous crystals 
project from the aggregate. We readily observe that the orange- 
yellow crystals form the greater part of the aggregates. If the crystals 
are investigated with reagents and solvents, differences become evident. 
When they are treated with sulphuric acid of 76°/, they all 
finally become blue, but the orange-yellow ones are coloured first. 
The red ones often retain their own colour for a long time. The 
1) Ricnarp WiustArrer und Watrer Mies, IV. Ueber die gelben Begleiter des 
Chlorophylis, Justus Liesia’s Annalen der Chemie, 355. Bd. 1907, p. 1. 
45* 
