ain species of insects that visit these flowers in search of nectar,
that provision for the cross-fertilization of the plants is insured, in
that the pollen from the anthers of one flower becomes lodged on the body
of the insect as it is withdrawing from the flower in such a way that it
comes in contact with the pistil of a second flower as the insect enters
it. Such flowers often have such peculiar shapes and lengths of nectar
tubes, etc., that only a single species of insect, whose anatomical shape
is "adapted" to that particular blossom shape can enter the flower in its
search for nectar. It is clear that this form of "morphological adaptation"
is a highly specialized one, which can only be the result of a long process
of evolutionary development. It is obvious that the plant cannot possibly
possess a mechanism, or ability, to alter its flower form in order to make
it conform to the shape and length of the proboscis, or other body parts,
of a particular species of insect. Either the insect or the plant, or both,
must go through a process of evolutionary development in order to arrive at
this form of mutual "adaptation."

A form of true morphological adaptation (in the sense in which we have been
using the term) is exhibited by many species of plants, which are provided
with many more buds, or growing points, than ever actually begin to grow.
For example, the single plumule which develops from a germinating wheat
embryo has at its upper end a hundred or more tiny growing points. At the
proper stage of its growth, several of these tiny buds begin to grow into
individual separate stems, and the new wheat plant thus produces several
stems from one seed and root system, a process known as the "stooling." The
number of stems in a single "stool" depends upon the number of the
potential growing points which are stimulated into growth. It varies from
only two or three up to as many as thirty or forty, and is apparently
controlled by the favorable or unfavorable conditions of climate or
nutrition at the time when the "stooling" takes place. The plant is thus
provided with a mechanism for adapting its possibilities of growth to the
supply of growth-promoting material which is available to it.

Many other plants produce far more buds than ever develop into growing
tissues, and buds which, under normal conditions, remain dormant, under
altered conditions start into growth and so provide for an "adaptation" of
the total mass of the