QUANTITATIVE LAWS IN REGENERATION. 

 III. The Quantitative Basis of Polarity in Regeneration. 



By JACQUES LOEB. 



(From the Laboratories of The Rockefeller Institute for Medical Research.) 



(Received for publication, January 18, 1922.) 



I. introduction. 



It has been shown in preceding papers that the dry weight of shoots 

 and roots produced under equal conditions of illumination, moisture, 

 and temperature in sister leaves of Bryophyllum calycinum varies 

 approximately in direct proportion with the dry weight of the leaves; 

 and that the same is true for the mass of shoots produced in small 

 pieces of stem connected with a leaf .^ It had been known that 

 when a piece of stem is left in connection with a leaf, the mass of 

 shoots produced by the leaf is less than when the leaf is completely 

 isolated, and the writer had been able to show that in this case the 

 stem connected with the leaf gains approximately as much in dry 

 weight as the dry weight of the shoots and roots in the leaf would have 

 been if the leaf had been completely isolated from the stem.^ The 

 inhibitory influence of the stem on the shoot and root formation in the 

 leaf was in this case due to the fact that when the leaf is connected 

 with a stem, that part of the material which could have been utilized 

 for the formation of new shoots and roots in the leaf now goes into the 

 stem. It is intended to show in this paper that the same simple 

 quantitative relations suffice to account for the polar character of 

 regeneration in a defoUated stem of Bryophyllum.^ 



The reader will remember that each node of the stem of this plant 

 has two dormant buds capable of growing into shoots. When a piece 

 of defoliated stem is cut from a plant and suspended in moist air, only 



^Loeb, J., J. Gen. Physiol, 1918-19, i, 81; 1919-20, ii, 297, 651. Science, 

 1917, xlv, 436. Bot. Gaz., 1918, xlv, 150. Ann. Inst. Pasteur, 1918, xxxii, 1. 

 2Loeb, J., /. Gen. Physiol, 1919-20, ii, 297, 651. 

 3 Loeb, J., Science, 1921. liv, 521. 



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