The Colouring-matters of 
[April, 
202 
published in the “ Verhandlungen der Physik. Med Gesell- 
sch aft zu Wurzburg” (vol. xvm.), and in the Natur- 
f 0 r it h a e nnears that a relatively small number of pigments 
serves for the produ«ion of the seemingly endless variety of 
colour in* flowers and fruits. The white and black shades 
which we encounter there are not due to any especid 
colouring-matter. White is due merely to the reflection of 
light through colourless tissues containing air. blacks 
their origin merely to the dense concentration of violet pig- 
ments. If we set aside chlorophyll green, which is raie y 
met with in flowers [but in fruits ?J , we may recognise t 
three following groups of colours : — i, yellows ; 2, reds , a 
3 ’ As “^"preitoull'y demonstrated by Hildebrand, the yel- 
lows are mostly in combination with the plasm.c substance, 
whilst the colours of the second and third group are gene- 
rallv found existing in solution in the cell-sap. 
The" yellow of flowers forms an insoluble compound with 
fatty matters, as was demonstrated by Krukenberg in ie 
animal kingdom under the name of lipochrome. [This 
circumstance may go far to account for the ge :nera ^onipa- 
rative permanence of the yellow colours both of plants and 
animals.] The yellow pigment obtained by Hansen in a 
pure crystalline state, by saponification with soda and ex- 
traction with petroleum ether, agrees in its behaviour with 
the hpochromes. The speAra of the pigments of different 
yellow flowers agree with each other so closely as to lead to 
the conclusion of their mutual identity. Between the I 
and G lines there occur two absorption-bands, which do not, 
however, always occupy exactly the same position. 1 he 
solutions are not fluoiescent. • 
Orange is formed by a denser deposit of the yellow pig- 
ment. Thus the colour of the rind of an orange is due to 
The same pigment as is found in the yellow flowers of 
Ranunculus repens. . . , 
The colour of yellow dahlias and of lemon-rind is not a 
lipochrome. It is soluble in water, and behaves differently 
both chemically and spectroscopically, displaying, 101 in- 
stance, no absorption-bands. It !s very similar vO the pig- 
ment of TE thulium septicum examined by Krukenberg. 
The reds of flowers may be reduced to a single pigment, 
—the rose-dye of roses, carnations, peonies, &c It is 
soluble in water, and is decolourised by alcohol, piobably 
consequence of dehydration. On the addition of an acid 
the colour is restored. The speCtrum displays a bioad 
