254 J- ARTHUR HARRIS AND H. S. REED. 



The graphs for the first, fourth and seventh increment show 

 clearly the shift in the position of the maximum positive corre- 

 lation from the earlier to the later periods as the " first variable " 

 is chosen from the later periods. The same is shown less clearly 

 by the correlations for the tenth increment, but there the coeffi- 

 cients are very small, presumably because growth has practically 

 ceased. 



It is clear, therefore, that plants which are growing more 

 rapidly during any period of development will 'grow more rapidly 

 during a closely associated subsequent period of development but 

 that there is little or no relationship, or even a negative relation- 

 ship, between the rate of growth of the organisms studied at con- 

 siderably separated periods of time. 



Since the correlations for absolute growth increments are so 

 small for all except successive periods of time, it seems unneces- 

 sary to deal at present with the relative growth increments, i.e., 

 with the growth increments expressed as a fraction of the size of 

 the organisms at the beginning of the growth period. 



PROBLEM 3. The correlation between the absolute sise of the 

 organism at given stages of development and subsequent growth 

 increments. 



In the higher plant organism rate of growth at any period 

 must be supposed to depend to some extent upon plastic ma- 

 terials synthesized by the more nearly mature portions of the 

 same individual. Thus one might expect to find a relationship 

 between the actual size of the organism at any stage of growth 

 and the rate at which the organism increases in size during a sub- 

 sequent period. 



We have determined the possible correlations between the ab- 

 solute size of the organism at different periods and the growth 

 increment of the organism during subsequent growth periods. 

 The coefficients are presented in Table V. This shows positive 

 correlation between the actual size of the organism at every stage 

 of development from the 7th to the 7Oth day and the increase in 

 the size of the organism during the following week. The mag- 

 nitude of the correlation is of the order ?- = o.45 to r==o.6o for 

 the Jth, I4th, 2ist, and 28th day. For these growth stages the 

 correlation between actual size and the subsequent growth incre- 



