352 BOTANICAL GAZETTE [NOVEMBER 
Finally, the difficulties of distributional, as of other physio- 
logical problems, are greatly aggravated by the fact that each 
organism is always in process of internal alteration, passing thus 
through various more or less well defined and conveniently sepa- 
rable phases of development. Thus, a certain quality, intensity, and 
duration of the light condition may be wholly without sensible 
effect upon an unsoaked seed, while the same dimensions of the same 
factor may be fatal to the same plant when in a more active develop- 
mental phase. In the study of external conditions it is thus useless 
to attempt to establish relations between these and organisms, 
unless adequate consideration is given to internal conditions or 
developmental phases of the latter. Quantitative ecology must not 
only try to find out to what environmental conditions its organisms 
are subjected, and to what degree and for how long these conditions 
are present, but it must also determine during what developmental 
phases of the organisms the conditions are effective. It is this 
consideration which makes it quite impossible to establish ecological 
relations without adequate knowledge of the physiological nature, 
at different developmental stages, of the forms dealt with. 
Leaving temporarily out of account those mechanical conditions 
which may, in the past, have acted to transport plants from one 
geographical area to another, we are aware that the environmental 
conditions which control growth and reproduction, after the intro- 
duction of an organism into a given region, are nearly always 
naturally in a state of flux. Day and night changes and the march 
of the seasons, together with more markedly irregular fluctuations 
in wind, precipitation, evaporation, etc., all produce their effects 
upon both living things and non-living ones, but these effects are 
usually much more pronounced in the case of organisms than in that 
of inanimate objects. As has been previously emphasized by one 
of the writers, an organism furnishes, at any instant, a summation 
of the effects of all the processes which have gone on in the body 
during its previous developmental history. One of our greatest 
difficulties, however, lies in the fact that we are totally unable to 
differentiate this integrated record, but we may nevertheless be 
3 Livineston, B. E., Climatic areas of the United States as related to plant 
growth. Proc. Amer. Phil. Soc. $2: 257-275. 1913. 


