510 Townsend . — The Correlation of Growth 
while previous investigators have concerned themselves for 
the most part with final results. 
It is well known that the removal of some of the branches 
of a tree will often cause the other branches to become more 
vigorous and the fruit to be more perfectly developed ; also 
that the disturbance of the roots of garden-plants, through 
the process of cultivation, often causes a more vigorous and 
rapid development of all their parts. However, no systematic 
study of injured plants has heretofore been made, in regard 
either to the effect of a single irritation of short duration 
or to the time required for such effect to manifest itself. 
Material and Methods. 
As far as possible in the experiments herein described, the 
external causes of the variation of the rate of growth were 
eliminated in order to study more accurately the internal 
influence of the irritation. With this object in view the 
plants were grown in damp chambers, in diffused light, and 
in all possible cases at a constant temperature. 
The larger number of the experiments were performed 
with seedlings. Satisfactory results were obtained with 
seedlings of Phaseolus multiflorus , Vicia Faba , Lupinus albus , 
Helianthus annuus , Cucurbita Pepo , Zea Mais , Arena sativa y 
Hordeum vulgar e , and Secale cere ale. Experiments with 
older plants were carried on with the same material, also 
with Calla , and with a few cuttings of Salix. A number of 
experiments have also been performed with Phycomyces nitens. 
Seedlings. — The seeds were soaked for about twenty-four 
hours, and then placed in damp sawdust at the temperature 
under which the experiments were to be carried on 1 . When 
the roots and shoots had attained the desired length, the 
seedlings were placed in glass boxes containing damp saw- 
dust, or the seeds were wrapped in damp cotton, and the 
roots were suspended in water or in damp chambers. In 
1 True, On the Influence of Sudden Changes of Turgor and of Temperature on 
Growth ; Annals of Botany, Vol. ix, p. 363, 1895. 
