fixed laws of plant
life, there are occasional deviations from it. A plant which, under normal
conditions of growth, develops in a certain fixed way, when exposed to
unusual environmental conditions, may, and often does, alter its habit of
growth in what may metaphorically be said to be an attempt to adjust itself
to the new conditions. Numerous examples of this phenomenon might be cited.
Certain algae, which grow normally in water at a temperature of 20 deg. to
30 deg. and which are killed if the temperature rises above 45 deg., have
been grown for successive generations in water the temperature of which has
been gradually raised, until they produce apparently normal growth in water
the temperature of which is as high as 78 deg.; also, certain types of algae
normally grow in the water of hot springs at temperatures of 85 deg. to 90
deg., and others in arctic sea-water the temperature of which sometimes
falls to -1.8 deg. and never rises above 0 deg. C. This phenomenon of the
adjustment of a species of plants to new conditions, which in the case of
farm crops is sometimes called "acclimatization," is of common occurrence
and is often utilized to economic advantage in the introduction of new
strains of crops into new agricultural districts. Again, the normal
development of plants may be altered as the result of injury or
mutilation. Thus, if the ear is removed from the stalk of Indian corn, at
any time after flowering, there always results an abnormal storage of
sucrose in the stalk, instead of the normal storage of starch in the
kernels. Similarly, midsummer pruning of fruit trees generally results
in the production of abnormally large number of fruit buds on the
remaining limbs. Many other familiar examples of alteration of normal
development in response to, or as the result of, abnormal conditions
of growth might be cited.

TYPES OF ADAPTATIONS

To designate these different alterations of normal growth, several
different terms have been used. Among these, "adaptation," "accommodation,"
and "adjustment" have been commonly used by different biologists. Sometimes
these are used interchangeably, and sometimes different terms are used to
designate different types of response to altered conditions of growth.
Inasmuch as there seems to be no generally accepted usage of these
different terms, only one of them, namely, the word "adaptation" will be
used here; and different manifestations of this ph