268 
Pearsall.—Studies in Growth. 
does not appear that the supply of nutrient salts was the limiting- factor. 
The assumption that the stem was almost monopolizing the organic food 
supply, to the partial exclusion of the roots, seems best to fit the facts, and 
one would then expect the stem to go on growing after root growth had 
ceased, a significant feature of all the cases investigated. 
The question can be considered from an entirely different standpoint. 
Fig. 4. Growth of stem and root (Series V) in 
peas after appearance of secondary roots. (Rate curves 
above.) Stem weight reduced by one-half. 
After secondary root development, the total area of root meristem 
possessed by a plant is increased enormously and the rate of growth of the 
roots might therefore be expected to increase proportionately. 
An examination of the rates of growth (by volume) before and after 
secondary root development in Series I (Nos. 2 and 3) shows that this is not 
the case, and a similar result is apparent when the following table is 
examined. This table shows the average growth rate of pea roots before 
and after secondary roots appear. 
