EXPERIMENTS IN THE HEREDITY OF PEAS. 



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EXPERIMENTS IN THE HEREDITY OF PEAS. 



By Charles C. Hurst, F.L.S., F.R.H.S. 



The following is a preliminary account of a series of experiments com- 

 menced in 1902 with garden Peas (Pisum sativum). The primary object 

 was to repeat Mendel's original experiments as closely as possible, and 

 test his principles of heredity. (Mendel 1865, Bateson 1901.) The second- 

 ary object was to endeavour to ascertain more fully the precise nature of 

 Mendel's categories of seed shape and cotyledon colour in Peas. (Cf. 

 Weldon 1902.) 



[For a translation of Mendel's original work, see R.H.S. Journal, 

 vol. xxvi., pages 1-33, 1901.] 



Seed Shape. 



For many years it has been the custom in gardens to divide the 

 ordinary races of white -flowered Peas into two classes, "Round" and 

 " Wrinkled." In the "Round " class are included all those with round, 

 roundish, or rounded seeds, the surface of the seeds being either quite 

 smooth or slightly pitted. In the " Wrinkled " class are included all those 

 with angular, squared, or flattened seeds, the surface of the seeds being 

 deeply dented, broadly wrinkled, or shrivelled. The precise nature of 

 wrinkling in Peas does not yet appear to have been determined, but Mr. 

 Bateson cites the analogous case of Round and Wrinkled Maize, in which 

 the " Round seeds contain much unconverted starch, while in the 

 Wrinkled or Sugar-maize this seems to be converted in great measure as 

 the seed ripens ; with the result that on drying the walls collapse. In 

 such seeds we may perhaps suppose that the process of conversion, which 

 in round seeds takes place on germination, is begun earlier, and perhaps 

 the variation essentially consists in the premature appearance of the con- 

 verting ferment." (1902, p. 123.) 



Mr. Bateson proceeds to say that it would be rash to suggest that such 

 a process may be operating in the Pea ; but when we consider that 

 wrinkled Peas are usually sweeter than round ones and will not germinate 

 so well as round ones if sown too early, and in a dry state do not 

 retain their vitality so long as round ones, it seems probable that the 

 nature of wrinkling in Maize and Peas may not only be analogous but identi- 

 cal. It is to be hoped that the chemists will take the matter up and 

 ascertain the precise nature of Round and Wrinkled Peas. In carrying 

 out my experiments I have been much impressed by the observation of 

 the powerful influence of the conditions of life on seed shape in Peas, and 

 though my evidence is not yet complete, I think that there is no doubt 

 that some, at all events, of the angularity, squareness, flattened sides and 

 deep dents are directly caused by the pressure of the Peas against one 

 another in the pod, and also by the constriction of the pod itself. I find 

 that, as a rule, the roundest Peas are small, or have plenty of room in the 



