CHAP. XVI. 
COLOUR. 
433 
the xanthic series, yet they are so far conformable to nature 
as to help us either in searching for the causes of colour, or 
in predicting the possible varieties of colour in flowers of the 
same species, and sometimes of the same genus. 
Messrs. Schiibler and Funk, considering green as the 
common colour of plants, have attempted to show that 
other colours are modifications of it, regarding all devia- 
tions as owing to the admixture of acid or alkaline secre- 
tions, an opinion in which they have been supported by 
Macaire Prinsep, whose views are adopted by De Candolle 
and others. But Macquart asserts (Die Farhen der Blilthen^ 
1835) that the chemical theory of Macaire Prinsep is 
erroneous, and offers quite another explanation of the nature 
of the changes in vegetable living colours. To understand 
this, it is necessary to consider the general nature of vege- 
table fluids, and especially what is really the colouring matter 
of plants. 
Crude sap is colourless, and to a certain extent it remains 
so to the end of the existence of a- plant, filling the cells and 
many of the intercellular passages. But by degrees it 
becomes altered, and gains the green colour which is called 
chlorophyll. This is in some cases a mere gelatinous mass 
lining the cells, or arranging itself in certain definite forms 
in different plants : in transverse zones in Conferva zonata 
and others, in spiral bands in Spirogyra, and in the form of 
gelatinous threads in many succulent plants; or it acquires a 
distinctly granular appearance. In the latter case, Mohl 
states that it is unilormly collected round a grain of starch, 
which forms its nucleus, or round several grains, as may be 
ascertained by testing the chlorophyll with iodine. That this is 
often so, may be easily seen by any one accustomed to delicate 
microscopical investigations. But I do not find the starch 
constantly inside the grains of chlorophyll ; on the contrary, it 
is certain that in some instances, as that of Cattleya Forbesii, 
they are external to the chlorophyll. I have counted as many 
as nine embedded in the circumference of a single grain of 
chlorophyll in this plant. 
This chlorophyll, although so abundant in plants as to be 
the exclusive cause of their green colour, is nevertheless. 
F F 
