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QUANTITATIVE LAWS IN REGENERATION. I 



of the piece of half stem at the beginning, bi the dry weight of the 

 piece of half stem at the end; then we should expect the following 

 relation to hold (within the limits of accuracy of the experiments). 



a — ai = bi — b 



Six sets of experiments (each with twelve pairs of leaves) were 

 made in which the dry weights of the shoots and of the pieces of 

 stem were determined. The stems were either 2, 4, or 8 cm. long, 

 and with this length of stem the formation of shoots on the pieces 

 connected with the stem was almost completely suppressed. The 

 weights of the roots were not determined but we know that on the 

 average the dry weight of the roots formed by the leaves under the 



conditions of our experiments is 42 per cent of the dry weight of the 

 shoots formed. Hence we must add this value in our final results 

 to a (but not to ai, since practically no shoots or roots were formed 

 in the leaves connected with the stems). Table VI gives the dry 

 weight determinations for the six sets of experiments. The dry 

 weight of the shoots produced by all the detached leaves in the 

 six sets of experiments is 1.270 gm. To this value must be added 

 the dry weight of the roots produced which amounts to 42 per cent 

 of the dry weights of shoots; namely, 0.533 gm. The value for a 

 then is 1.270 + 0.533 = 1.803 gm. 



The value for ai -\- bi — b was equal to 1.891 gm. Practically no 

 shoots or roots were produced by these leaves connected with their 

 stems, so that no correction for roots is necessary. Hence the value 



