PRESENT PROBLEMS OF PHYSIOLOGICAL 

 PLANT ECOLOGY 

 DR. BURTON E. LIVINGSTON 

 Desert Botanical Laboratory 



By physiological ecology is here meant merely the 

 study of the factors which determine the occurrence and 

 behavior of plants growing under uncontrolled conditions. 

 Field physiology would be almost a synonym for the 

 term here used. Pure physiology proceeds, as far as is 

 possible, by controlling conditions. By varying known 

 conditions and measuring the plant responses definite 

 relations are established between stimulus and response. 

 But ecology must perforce proceed without the known 

 conditions, without the synthetically built-up environ- 

 ment of pure physiological research. Here it is neces- 

 sary to measure and analyze natural conditions and to 

 relate these to the behavior of the plants. The problem 

 of measuring the plant phenomena, the determination 

 of the number, size, form, structure, etc., of the plants 

 involved, is essentially the same for both lines of study, 

 but that of measuring environmental conditions is, of 

 course, much more difficult where the latter are uncon- 

 trolled. 



There is a principle of scientific research, that in an 

 investigation which involves the measurement of a num- 

 ber of causal factors and the relation of these factors to 

 resulting conditions, the various measurements should be 

 of as nearly equal accuracy as possible. Where a num- 

 ber of complex factors are to be dealt with, as in ecology, 

 progress must come, on the one hand, from a refinement 

 of methods of measurement and, on the other, from better 

 interpretations of the data resulting from these measure- 

 ments. According to the principle just stated, we should 

 ever seek to improve those of our methods which are the 



