30 KANSAS ACADEMY OF SCIENCE. 
cellent observations were relegated to obscurity by the upper crust of botanists — 
the systematists who did not care to waste their time on such amateur work. 
While ecological observations are scattered here and there through later 
botanical writings, they lacked coherence, and this branch was constantly handi- 
capped by the theory of the fixity of species. It remained for Charles Darwin to 
bring order out of chaos and give us a working theory of development. His in- 
vestigations may be said to have laid the foundation of ecology. It is needless 
to dwell upon the theory of the Darwinian school, but ecology owes its impetus 
to the recognition of the plasticity of species. The study of adaptability has 
been so active and the mass of facts accumulated has been so great that it was 
recognized as a distinct branch of botanical science, first under the name of 
biology and later under the name of ecology. Let us now take a look at a brief 
classification of the subjects included. It will be seen at once that ecology isa 
study of life relations—the relations of the plant to its environment. The factors: 
which influence the plant from without are known as ecological factors, and may 
be arranged for the most part in the following groups: 
WATER. AIR. ANIMALS, 
Heat. Solt. OTHER PLaNTs. 
LIGHT. 
The fact that a plant thrives where it is shows that it is adapted to the condi- 
tions, and that an equilibrium has been established between the plant and the 
factors normally surrounding or affecting it. 
WatrErR.— Water is a vital necessity. The variation in the water-supply causes. 
corresponding variations in the structure. In submerged plants the water with 
the containing mineral matter is absorbed directly. Hence there is no transpira- 
tion current, and the roots have no absorptive function. Roots when present are 
fastening organs. If the leaves are floating or emerged there is set up a transpi-. 
ration current which must be supplied from beneath by the absorptive action of 
the roots. In all land plants a transpiration current is necessary to supply the 
mineral matter from the soil. It is not often that the soil conditions and air 
conditions are so evenly balanced that the plant is free to take up and evaporate 
all the water it needs for the most rapid growth. In some cases, on account of 
the saturated atmosphere, there is danger from a stagnated transpiration cur- 
rent, and the plant endeavors in various ways to aid evaporation. Experiments 
have shown that an individual plant can be profoundly modified by a change in 
the water relation. A normally xerophytic plant with rosette foliage can be- 
made to stretch out its axis, to broaden its leaves, and otherwise take on the 
structure of a hygrophyte. To indicate the nature of the problems presented I 
will suggest a few adaptations, some proved by experiment, others still hypothet- 
ical. In the rain forests of the tropics the leaves are often provided with long 
points and converging veins to lead off the water easily. Mottled leaves in which 
irregular areas lack chlorophyll increase the evaporating surface without in- 
creasing that engaged in photosynthesis. The presence of the red coloring mat- 
ter on the under surface of floating leaves may be for the purpose of converting 
the waste light into heat, thus slightly raising the temperature of the leaf and 
enabling it to evaporate, when otherwise the air would be saturated and prevent 
evaporation. Glands which excrete liquid water are common. On the other 
hand, in dry regions the plant is obliged to prevent evaporation as much as pos- 
sible, without entirely suppressing the transpiration current. There are numer- 
ous and curious methods by which plants protect themselves from drought. 
Heat.— Plants are rarely injured by the high temperature to which they are: 
subject in nature, provided the water-supply is not reduced. But, except in the: 
