RESEARCH METHODS IN STUDY OE EOREST ENVIRONMENT. 9 
a sufficient affinity for water and a sufficiently close chemical combi- 
nation to enable this embryonic plant to resist all of the forces of 
disintegration during a period of dormancy. 
The first requirement, then, is that the present plant should live 
long enough to accumulate by absorption from the soil a quantity of 
phosphorus which may be concentrated in this one seed, or ten 
thousand seeds, as the case may be. 
To accomplish this object, it is rather evident that a large amount 
of water must be absorbed and disposed of, with a resulting deposit 
of phosphorus and other solids as the water is evaporated. Even 
then there must be a strong tendency for such solids, if retained in 
solution, to diffuse back to the roots and into the soil. Not denying 
the possible ability of the plant to trap and hold phosphorus, or any 
other needed substance, at the point where needed, it seems necessary 
to call into play some other physical force to effect this concentration. 
The only other possible force is the electromagnetic affinity of energy 
for matter and of matter for energy. The ability of the plant to 
concentrate the essential inorganic substances in the best-lighted 
parts of its structure may thus be explained. 
In other words, the requirement of plants for light is primarily a 
requirement for a concentration of essential substances needed for 
reproduction. But light can only be obtained Avhere there is com- 
petition through growth. To insure the necessary amount of light, 
the individual plant is required to keep its head at least up to the level 
of the competitors, and the plant which becomes dominant is most 
certain to reproduce. Possible differences between plants, in their 
ability to make use of different kinds of light, need not be discussed 
here. 
So, then, reproduction requires light, the need for light calls for 
growth, and growth in turn is possible only through the action of 
light in photo-synthesis, or the creation of new organic matter by the 
combination of water and carbon dioxide. 
This necessary combination of water from the soil and carbon 
dioxide from the air can be effected only by exposing the cells con- 
taining water to the air, so that the carbon dioxide may be absorbed 
by these cells. The important feature ecologically is that such ex- 
posure inevitably results in considerable losses of water; and even 
though the cells so exposed may be somewhat protected, it is evi- 
dent that carbon-dioxide absorption and water loss must, in a given 
plant, run about parallel, both being controlled by the size of the 
stomatal openings. The actual water loss, of course, will vary ac- 
cording to the dryness of the air, the concentration and vapor 
pressure of the contents of the exposed cell, and the intensity of the 
light in which the operation is performed. Thus a plant capable of 
making use of diffused light, or largely of the so-called actinic rays, 
