No. 640] BODY SIZE AND ORGAN SIZE 



401 



The present study emphasizes the difficulties lying in 

 the path of the investigator who attempts to solve such 

 a problem as this merely by determining a single series 

 of biometrical constants without taking into account the 

 various morphological and physiological factors which 

 may be involved. 



Summary 



1. The problem of the relationship between the size 

 of the plant body and the size of the organs it produces 

 has been studied by various workers, who find that in 

 most cases there is a small but significant correlation 

 between these characters. 



2. In a series of bean plants, the coefficients of cor- 

 relation were determined between plant size, as meas- 

 ured by dry weight of shoot, dry weight of fruit, number 

 of leaves, number of pods and number of seeds ; and the 

 average dry weight per plant of leaf, pod and seed. A 

 positive and significant correlation, though usually a 

 small one, was found in each case. 



3. An examination of the curve of means for organ 

 size on plant size shows that in each case the curve rises 

 steeply at first and then flattens out. In other words, 

 an increase in the size of the plant is accompanied by 

 an increase in the size of its organs if we consider com- 

 paratively small plants only; but after a certain size 

 is reached, any further increase in plant size is not 

 followed by increase in organ size. Separate correla- 

 tions between plant size and organ size made for small 

 plants (those below the point where the curve flattens) 

 and for large ones (those above it) showed a very de- 

 cided correlation in the former and practically none at 

 all in the latter. 



4. These facts suggested that the size of an organ may 

 not bo correlated with body size at all, but rather with 

 the size of tlio axial i,n-owing point from which it develops. 

 In siii)}>ort (.r tliis idea attention is called to the fact 

 that diirin.ii- the early sta.ues of a plant's growth there is 



