Page:Popular Science Monthly Volume 84.djvu/423

Rh The relation of plants, and of all organisms to water, is, therefore, a fundamental one, and it is to the determination of these and other important environic relations that a large share of the attention of the department of botanical research is directed. If this conception has been properly formulated you will be prepared to receive without surprise the statement that the Desert Laboratory as the principal instrument of research of this department was not established primarily for the purpose of making studies upon desert vegetation as such.

There is no adequate foundation for a science devoted to the organisms which live in arid regions. There is no more a desert botanical science than there is a mountain astronomy. The physicist seeks and selects a place for the operation of his instruments in which observations and experiments may be carried on to the best advantage. The biologist takes one of his laboratories to the seashore and another to the desert, because here in these places organisms carry on the various processes in tissues of diverse structure and at different rates, and extended facilities for experimentation and widened angles of observation are made possible.

If to these statements as to the purpose and general scope of our researches, a few words be added as to the view-point taken as to the constitution of living matter itself, we may then profitably proceed to a discussion of the main thesis of the present paper.

Protoplasm is characterized by the fact that it includes an enormous number of compounds of carbon, oxygen and hydrogen, which sustain comparatively simple (chemical) structural relations to each other and most of which are highly unstable. These two features make possible variety and complexity in the mechanical structure and composition of the tissues of plants and animals, give opportunity for the occurrence of a multiplicity of chemical transformations in metabolism, and render all the functions of the organisms highly modifiable.

Any sense of daze we may experience from a contemplation of the number of things, or combinations in protoplasm, however, is not a logical excuse for going into the haze of vitalistic notions upon which much of the pedagogical practise and speculative writing in biological science of the present time is based. Ten, or ten million, the components of protoplasm act in accordance with a few fundamental physico-chemical laws. Complexity of composition yields in importance to the types of energy transformations displayed, and to the external expression of what are known as the biological activities as they may be modified by the environment.

The plant may be profitably visualized as an upright cylinder of watery gelatine surrounded by a semi-permeable tubular casing. The lower extremity of this cylinder is ramified into roots which are in intimate contact with moist soil-particles, so that the water in the body of