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DEPARTMENT OF AGRICULTURE 

 Vol. V WASHINGTON, D. C, D^cembejr 6, 1915 No. 10 



INHERITANCE OF LENGTH OF POD IN CERTAIN 



CROSSES 



By John Belling/ r .r>,^ 



Assistant Botanist, Florida Agricultural Experiment Station f^hW' », 



INTRODUCTION , '-'^^'C^^ 



The inheritance of a difference between two plants has sometimes, 

 though not often, been studied both quahtatively and quantitatively. 

 Correns (5) ^ has shown that this can be done even with differences in 

 flower color. The inheritance of a large-size difference can occasionally 

 be followed by mere inspection, as in crosses of some tall and dwarf 

 races of peas {Pisum sativum) (13); sweet-peas {Lathyrus odoratus) 

 (i, p. 280-281); beans (Phaseolus vulgaris) (8); and maize (Zea mays) 

 (10). 



Even -with accurate measurements, however, it will probably not be 

 possible to keep track of a single small-size difference, for its segregation 

 may be masked by the modifications. But if several small genetic 

 differences affect the size of the same plant organ, it would usually be 

 still less possible to disentangle the segregation in the second generation 

 of a cross, as Johannsen (12) has proved. The masking effect of the 

 modifications may, however, be lessened by choosing those plant organs 

 which are least liable to modification and which are also repeated many 

 times on each plant , such as flowers (6) or pods with the modal number 

 of consecutive ripe seeds (2). In one such case some of the members 

 of a fraternity were grown on poles 8 feet apart, and others were sown 

 at inten^als of 4 feet in a thick row of sorghum. Though the crops of 

 the stunted plants averaged only one-twentieth of those of the others, 

 yet the average length of their 5 -seeded pods reached 94 per cent of that 

 of the pods of the well-nourished plants. 



In the reciprocal crosses described in this paper, the length of pod was 

 first studied qualitatively and then quantitatively. All the families 



' I express my thanks to Messrs. C. D. Gunn and C. W. Long, of the Florida Experiment Station, for 

 their careful work in measuring pods. 

 2 Reference is made by number to "Literature cited," pp. 419-420. 



Journal of Agricultural Research, Vol. V, No. 10 



Dept. of Agriculture, Washington, D. C Dec. 6, 1915 



au Fla.— I 



(40s) 



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