COLORS OF VEGETATION. 69 
tional to the amount of luminous fluid—light, which is present.” 
This decomposition can take place only in the presence of sun- 
light and chlorophyl, but there are many parts of plants in which 
chlorophyl is entirely wanting and which develop in the absence 
of light, yet which nevertheless are brightly colored. Roots and 
tubers are often of brilliant hues, as in the carrot and gold-thread. 
So also the inner wood of a tree, as in the magnolia and rosewood. 
These colors are formed in the presence neither of sunlight nor 
chlorophyl, so there must exist other causes of coloration than 
that allowed in the theory of Macquart. 
Again, although submarine vegetation is usually of a dull green 
or brown, we find many seaweeds which are brilliantly tinted, 
although they receive but a very feeble light. Although chemical 
analysis throws some light on the laws of vegetable chromatol- 
ogy, yet the color ofghe flowers cannot in general -be taken as 
any index of the medfal properties of plants, for we may find 
the same colors at once in the most poisonous herbs, as fox glove 
and belladonna, and in the most innocent, as the aia and 
violets. 
The flowers of many plants are subject to changes in color. The 
closed gentian, for example, changes from a deep indigo-blue to 
a reddish-purple. The white Trillium becomes of a delicate rose 
color just before it withers. The ray flowers of Xeranthemum are 
straw color when they first expand becoming, at last, of a bright 
crimson. A more striking example is the Gladiolus versicolor 
which is brown when it opens in the morning, changes to a clear 
blue in the noonday sunshine and returns to brown again at night 
to go through the same variations the next day. 
Black as a color exists in vegetation only in the roots, seeds 
and a few fruits. It does not occur in the flowers. All the ap- 
proaches to it, as in the case of the dark spot on the corolla of the 
coffee bean, are simply an intense violet. There are no flowers 
of a pure white. The famous flower painter Redouté, observed 
long ago that in flowers which appeared white, there is always a — 
faint tinge of rose color, yellow or blue. When a white petal is 
viewed by transmitted light we see various shades produced by 
some coloring matter present in the cells in a state of extreme 
dilution. White frequently with a tinge of pink is the most com- 
mon color in spring flowers and in flowers of Arctic regions. Red 
is the hue of summer flowers and of acid fruits; bright red is rarely _ 
