266 BOTANICAL GAZETTE [october 



axillary bud is inhibited by its own leaf and there are no active 

 growing tips to inhibit the direct action of the water in inducing 

 bud development in the experimental leaf. Isolation from an 

 active growing tip is the chief factor in the development of the 

 leaf buds, and such isolation exists to a greater degree in Loeb's 

 first and third experiments than in the second, in which the axil- 

 lary bud of the opposite side starts before the leaf buds of the 

 experimental side. These three experiments, therefore, instead of 

 disproving, as Loeb asserts, that isolation is the factor initiating 

 development of the leaf buds, constitute evidence in support of 

 the conclusion that it is such a factor. Moreover, according to 

 Loeb's later assumption of inhibiting substances, it would seem 

 that isolation must be the initiating factor. 



The chief results of the paper are summarized as follows. The 

 cooling of a zone of the petiole of the Bryophyllum leaf to a tem- 

 perature of 2.5 to 4 C. for a few days is a very effective means of 

 inducing the outgrowth of the leaf buds. Usually the opposite 

 leaf and often leaves of adjoining nodes also show more or less 

 development. The passage of fluids to the leaf is not appreciably 

 interfered with by the cooled zone; therefore it seems improbable 

 that physiological isolation of the leaf can be due to the blocking 

 of passage of inhibiting substances transported in these fluids. 



University of Chicago 



LITERATURE CITED 

 1. Child, C. M., Studies on the dynamics of morphogenesis, etc. J 



2. 



Zool. 11:187-220; 221-280. 1911. 



, Die physiologische isolation von teilen des organismus. Vort 



und aufs. u. Entwickelungsmech. 11:157. 1911. 



3- — , Individuality in organisms. Chicago. 191 5. 



4- , The gradient in susceptibility to cyanides in the meridional con- 

 ducting path of the ctenophore, Mnemiopsis. Amer. Jour. Physiol. 



41. 1917- 



5- , Differential susceptibility and differential inhibition in the develop- 

 ment of polychete annelids. Jour. Morph. 30: 1-63. 1917. 



6. , The nature and origin of the physiological gradients. Biol. Bull. 



39. 1920. 



7. Child, C. M., and Bellamy, A. W., Physiological isolation by low tem- 

 perature in Bryophyllum and other plants. Science 50:362-365. 1919. 





