LEAF- TISSUE PRODUCTION AND WATER CONTENT IN 



A MUTANT RACE OF PHASEOLUS VULGARIS 



J. ARTHUR HARRIS 



Introductory 



In a preceding paper 1 it was shown that the survival of the bean 

 plant is in a measurable degree dependent upon the morphological 

 .characteristics of the seedling. In 1915 a series of investigations 

 was undertaken to determine, if possible, something of the proximate 

 causes of the differential death rate. It was also hoped that some 

 light would thereby be thrown upon the proximate causes under 

 lying the occurrence of teratological variations in the seedlings of 

 Phaseolus. In undertaking this work the assumption seemed 

 justified that if innate physiological conditions which might affect 

 growth be associated with morphological variations, some influence 

 of these factors should be recorded in the size or other characteristics 

 which result from the relatively enormous expansion which the 

 organs of the embryo undergo in the course of germination and the 

 establishment of the seedling. 



A first study 2 demonstrated that teratological seedlings in 

 general show a lower capacity for the development of primordial 

 leaf tissue than do normal seedlings grown under as nearly as pos 

 sible identical conditions. The data then available indicated that 

 a reduction of the volume of primordial leaf tissue is associated 

 with abnormalities of all the abnormal types studied, but that the 

 type of variation influences in some degree the amount of reduction. 

 In these first experiments the conclusions were based on primordial 

 leaves only. The use of such leaves has the obvious disadvantage 

 that they are formed in the seed, and undergo merely an enormous 

 expansion (and possibly a little differentiation) in the germination 



1 HARRIS, J. ARTHUR, A simple demonstration of the action of natural selection. 



Science, N.S. 36:713-715. 1912. 



2 , Studies on the correlation of morphological and physiological characters: 



The development of the primordial leaves in teratological bean seedlings. Genetics 

 1:185-196. 1916. 



IS 1 ) [Botanical Gazette, vol. 72 



