44 
THE AMERICAN BOTANIST. 
readily soluble in ether. It also occurs in all foliage leaves 
though its presence is usually masked by the green pig- 
ment of the leaf. In many plants,' however, it is so 
^bundant that it gives a yellowish hue to the leaves. In 
a few flowers and fruits, as in the yellow dahlia and the 
peel of the lemon, the color is due to a yellow pigment 
dissolved in the cell sap and not to solid grains of carotin. 
In plants with golden yellow foliage, as in many conifers 
and various shrubs, still another yellow pigment has 
been found. 
White flowers are most common in our flora as well 
as in that of Europe. Many of the 955 white flowers in 
the territory under consideration belong to shrubs and 
trees. There is nothing more beautiful in the temperate 
zone than an apple orchard in bloom with its billowing 
banks of innumerable white blossoms, tinged with rose 
and flecked with the vivid green of the newly unfolding 
leaf buds. The cornels and viburnums are justly ranked 
among our handsomest shrubs. They produce large 
clusters of white flowers in such boundless profusion that 
the entire shrub is transformed into a huge bouquet. 
Small deUvSely clustered white flowers are also common in 
the mustard, saxifrage and carrot families. Nocturnal 
flowers are also usually white. 
White flowers contain no pigments. Like the snow 
and powdered glass they owe their color to their optical 
properties. To produce such vast numbers of blossoms 
must of course tax the energies of a plant, and the absence 
of pigments lessens this expenditure. Like w^hite leaves I 
believe that white flowers are the result of retrogression 
or degeneration. Any bright colored flower may occa- 
sionally revert to white. Whatever impairs the vigor and 
vitality of the plant as cold, impoverished soil, injury to 
the roots, or continued self-fertilization will cause the 
floral hues to become paler or change to white. I once 
transplanted a scarlet popp^^ when in bud and the flowers 
became much smaller and changed to pure white. On the 
other hand whatever stimulates the growth of a plant as 
