THE PHYSIOLOGICAL BASIS OF MORPHOLOGICAL 

 POLARITY IN REGENERATION. II. 



By JACQUES LOEB. 



{From the Laboratories of The Rockefeller Institute for Medical Research?} 



(Received for publication, April 17, 1919.) 



I. INTRODUCTION. 



The preceding papers have shown that the phenomenon of regenera- 

 tion of shoots in Bryophyllum calycinum is to be treated as a prob- 

 lem of nutrition and growth, since equal masses of sister leaves, when 

 cut off from the plant, produce under equal conditions and in equal 

 time approximately equal masses of shoots though the number of 

 shoots may differ considerably;^ and since stems split longitudi- 

 nally, each retaining one sister leaf, produce also approximately 

 equal masses of shoots in equal times and under equal conditions.? 

 When the masses of two sets of sister leaves are made unequal, 

 the mass of shoots produced by the leaf or by the stem varies ap- 

 proximately in proportion to the mass of the leaves. This law 

 holds only when the leaves are exposed to light and it seems difficult 

 to interpret it in any other way except that it is primarily the mass 

 of the material produced in or sent out by the leaf which determines 

 the mass of shoots produced in these cases. 



Phenomena of regeneration show a second characteristic which 

 we may designate briefly as that of morphological polarity, whereby 

 we mean that an isolated piece of a plant or animal will as a rule 

 produce different organs at opposite ends. If regeneration is a 

 phenomenon of nutrition or chemical mass action, it will also become 

 necessary to account for this polarity iii tenns of nutrition or mass 

 action. We have commenced an investigation of the physiological 

 basis of polarity and have published already some results which have 



1 Loeb, J., Bot. Gaz., 1918, kv, 150. 



2 Loeb, J., J. Gen. Physiol., 1918-19, i, 81. 



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