691 
Flowers: Chelidonium majus L., Corydalis lutea DC, Erysimum 
Perofskianum Fiscn et Mny., Isatis tinctoria L., Cytisus sagittalis Kocn 
(Genista sagittalis L.), Spartium junceum L., Thermopsis lanceolata 
R. Br, Cucurbita melanosperma A. Br., Doronicum Pardalianches L., 
Hiëracium aurantiacum L., Gazania splendens Horr., Asclepias curas- 
savica L., Calceolaria rugosa Hook., Dendrobium thyrsiflorum Rous. 
fil., Iris Pseudacorus L., Clivia miniata Rremr, Lilium croceum Cuarx, 
Hemerocallis Middendorffii 'Trautv. et Muy. 
Leaf of Urtica dioica L. . 
Fruits: Sorbus aucuparia L., Solanum Lycopersicum Try. 
Root of Daucus Carota L. 
Algae: Cladophora sp., Haematococcus pluvialis Fror. 
Lodine. 
With carotinoids iodine forms addition products. In about twenty 
cases the behaviour of iodine in potassium iodide solution was in- 
vestigated with respect to the crystals of the carotinoids. By means 
of the potash method the latter were separated out in most cases. 
With iodine they became nearly always green. Often they were 
distinctly green, in other cases less so, and frequently they were 
yellowish green. In many cases the green colour appeared immedi- 
ately, and sometimes not at once, but only gradually, as, namely, 
in the flowers of Chelidonium majus and Spartium junceum, and 
in the red erystals obtained in the flower of Asclepias curassavica 
and the leaf of Urtica dioica. Sometimes no green coloration what- 
ever could be observed, not even after 24 hours. This was so with 
the flower of Dendrobium thyrsiflorum where, in addition to orange- 
yellow crystals, aggregates of orange or orange-red crystals separated 
out, which did not became green. The objects experimented upon 
with iodine in potassium iodide solution were the same as those on 
which bromine water was tried. 
Solvents. 
The most suitable solvents for the microscopical investigation of 
the carotinoid crystals are those which can be mixed with water. 
The preparations can then be brought direct from water into the 
solvent or the solvent can be allowed to flow under a cover-slip to 
the preparations which are in water. Solvents which fulfil this 
condition are, for example, alcohol and acetone. In addition use can 
be made of an alcoholic soap-solution (soap-spirit of the Dutch Pharm. 
4h edition, without oil of lavender) and of chloralhydrate solution 
45 
Proceedings Royal Acad. Amsterdam. Vol. XIV, 
