Ill 
THE COLOURS AND PIGMENTS OF PLANTS 69 
in the amount of acid present in the cell-sap. Other 
plants again show an extraordinary constancy in the 
tint of the anthocyan of the petals, the fruitlessness 
of florists’ efforts to produce blue roses is said to be 
the result of some peculiarity of constitution of the 
pigment which makes the tint impossible. 
The colours of the lipochromes vary from yellow 
through orange to red, and they colour such flowers 
as daffodils, jonquils, yellow and red lilies, such fruits 
as those of the tomato, the melon, the honeysuckle, 
the asparagus, the lily-of-the-valley, and so on. It 
is interesting to note, however, that the pure red 
lipochromes, as distinct from the orange, are rare if 
not entirely absent in plants (see Chap. II. under 
Lipochromes). As to origin, the chromoplasts arise 
in‘much the same way as chlorophyll corpuscles do, 
and indeed in many cases the unripe fruit or un¬ 
developed floral leaves contain ordinary chlorophyll 
corpuscles. As development proceeds the chlorophyll 
disappears just as in the case of autumnal leaves, 
and the highly coloured lipochrome is left. Various 
names have been given to the different lipochromes 
of flowers and fruits, but there is some reason to 
suppose that they all arise from the pigments normally 
associated with chlorophyll. Sometimes the lipo¬ 
chromes occur in ripe fruits and flowers as crystals, 
the original envelope of protoplasm having entirely 
disappeared. The colours of most flowers and fruits 
are caused either by anthocyan or lipochrome pig¬ 
ments, or by a combination of the two, but there are 
a few which are coloured by a yellow pigment of 
unknown affinities dissolved in the cell-sap. Such are 
the colouring-matters of the orange and of the dahlia. 
