But this color is
not limited to the corolla. It is also to be seen in the stems and in
the stalks and veins of the leaves, which are stained with a deep
purple, the blue color being added to the original green. Even on the
surface of the leaves it may spread into a purplish hue. On the stems it
is to be met with everywhere, and even the young seedlings show it. This
is of some importance, as the young plants when unfolding their
cotyledons and primary leaves, may be distinguished by this means from
the seedlings of the white flowered species.
In crossing experiments it is therefore possible to distinguish the
whites and the blues, even in young seedlings, and experience shows that
the correlation is quite constant. The color can always be relied upon;
if lacking in the seedlings, it will be lacking in the stems and flowers
also; but if the axis of the young plant is ever so slightly tinged, the
color will show itself in its beauty in the later stages of the life of
the plant.
This is what we term correlation. The colors of the different organs are
always in agreement. It is true that they require the concurrence of
[144] light for development, and that in the dark or in a faint light
the seedlings are apt to remain green when they should become purple,
but aside from such consideration all organs always come true to their
color, whether pure green and white, or whether these are combined with
the blue tinge.
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