8 BULLETIN 1059, U. S. DEPARTMENT OP AGRICULTURE. 
Studies which do not involve continuous observations for a long- 
period of years or expensive stationary instruments and equipment — 
for example, microscopic and chemical studies of woods or studies of 
natural reproduction, distribution, and growth — may be conducted 
without permanent forest experiment stations ; and even observations 
on climate in its relation to forest vegetation may sometimes be made 
on short field trips. Very often the painstaking observer, without 
extensive apparatus, will discover some fundamental facts which alter 
the conception of a given problem, and which therefore lead to far 
more productive efforts by the permanent organizations which can 
study the problem for longer periods. It is only by recognizing this 
principle of supplemental effort that substantial progress in forest 
investigations can be made. There should be no attempt to delimit 
the work of any organization or individual. 
THE SIMPLE PHYSICO-PHYSIOLOGICAL CONCEPT. 
Many ecological problems are less confusing to the beginner and 
are more likely to be approached by sound methods if, at the outset, a 
rather definite physical interpretation of life is accepted, for through 
such a concept is gained an idea as to the probable physical reaction 
to the environment and the method of measuring the physical con- 
ditions. 
Thus, to begin with, the living mass of plants (the protoplasmic 
mass, primarily) may be conceived to be simply a colloidal mass of 
organic compounds with a peculiar affinity for water. Water is of 
fundamental importance to its life qualities. To supply the demand 
for water, the protoplasmic mass must possess a greater affinity for it 
than the soil or solution from which the water is to be obtained. The 
struggle for water is, primarily, a contest between the colloids of the 
plant and the organic and inorganic (clay) colloids of the soil. 
Secondly, it is inevitable that any object possessing water should 
lose the same by evaporation to the atmosphere until a balance is 
reached between the vapor pressure of the water-holding mass and 
that of the atmosphere. Such an equilibrium does not. necessarily, 
mean death, at least for certain kinds of tissues, but the small supply 
of water represented by equilibrium with ordinary atmospheric vapor 
is insufficient to permit photo-synthesis, metabolism, and transport 
within the plant. For continued functioning, the plant must be able 
to maintain its water supply above this level. 
The objective of physiological functioning is reproduction, to which 
growth is only incidental. The object in the existence of any indi- 
vidual plant is to extract enough phosphorus x from the soil so that a 
peculiar accumulation of matter called a seed may be formed.' with 
1 Phosphorus is mentioned only as an example of the vitally necessary elements ob- 
tained from the soil. 
