ON DIFFERENTIAL MORTALITY WITH RESPECT 

 TO SEED WEIGHT OCCURRING IN FIELD 

 CULTURES OF PHASEOLUS VULGARIS 



DR. J. ARTHUR HARRIS 

 Carnegie Institution of Washington 



Introductory Remarks 



In the rather voluminous literature of seed testing, 

 comparatively little attention has been given to the pos- 

 sible relationship between the characteristics of the seed 

 (or of the plant from which it was gathered) and its 

 viability. This is of course attributable to the fact that 

 such work has been done chiefly for immediately prac- 

 tical ends, the object being in most cases to determine, 

 by germination tests of a small sample, the suitability of 

 a given bulk of seed for commercial planting. 



To the student of natural selection, however, the car- 

 dinal problem of viability is to determine whether the 

 capacity for development of a seed is a function of its 

 patent or potential (i. e., of its own measurable or of its 

 inherent but as yet undeveloped) characteristics. A 

 satisfactory solution of this very complicated problem 

 would, I believe, be of rather wide interest. At the out- 

 set, however, one must fix clearly in mind that if a selec- 

 tive mortality be demonstrated, it has no necessary bear- 

 ing upon the question of the origin of species. Natural 

 selection may maintain a type already differentiated as 

 well as mould new forms but in order to do either the 

 variations upon which it acts must be heritable. But in 

 any case the results would be of interest to the physiol- 

 ogist concerned with the problems of the relationship 

 between form and function. Finally, exact information 

 on the relationship between structural characteristics 

 and viability— if they exist— may be of some practical 

 importance in agriculture and plant breeding. 



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