EXPERIMENTS IN THE HEREDITY OF PEAS 



493 



upon this simple Mendelian idea of unit-characters (also discovered 

 independently by Professor De Vries before he re-discovered Mendel's 

 long-lost paper, 1900 A, b). Naturally Mendel himself was only able to 

 touch the fringe of the subject in his experiments with Peas ; yet, by 

 making this one point clear, he has enabled his many successors to attack 

 the difficult and complicated problem in a new and analytical way. 

 Already, by the application of the Mendelian system of analysis 

 by experiment, there are signs that we are on the eve of some important 

 discoveries in heredity. 



Expt. 



Round Yellow. 



Round Green. 



Wrinkled Yellow. 



Wrinkled Gn 



2 



19 



8 



4 



2 



3 



24 



8 



3 



1 



4 



17 



7 



9 



2 



5 



281 



97 



93 



32 



6 



8 



7 



3 



2 



7 



109 



26 



25 



11 



8 



49 



13 



8 



4 



9 



161 



42 



44 



8 



10 



203 



84 



81 



26 



11 



62 



23 



22 



8 



12 



54 



18 



17 



8 



13 



10 



5 



4 



3 



Observed 



997 



338 



313 



107 



Calculated 



990 



330 



330 . 



110 



Mendelian 











ratio 



9 : 



3 



: 3 



: 1 



(Since the above was written, 1 find that Mr. R. P. Gregory, in a recent paper on 

 " The Seed Characters of Pisum sativum" (New Phytologist, 1903, December, p. 226, 

 rig. 1), shows clearly that the histological nature of a "Round" Pea is quite distinct 

 from that of a " Wrinkled " one. In a " Round " Pea the starch grains, stored in the 

 cotyledons, are large, few, and oval, while in a "Wrinkled" Pea they are small, 

 numerous, and irregular. 



In examining some of the "intermediate" and dubious shapes pointed out by 

 Professor Weldon in such irregular round races as ' Telegraph ' (1902, pi. II., figs. 1-4), 

 Mr. Gregory found no seed which, upon histological examination, allowed of any doubt 

 as to its round character. 



Mr. Gregory concludes therefore that pitting, false wrinkling, and other 

 irregularities in "Round" Peas must be distinguished from the true wrinkling in 

 " Wrinkled " Peas, and that the latter must be the expression of a distinct physiological 

 process. These important histological observations show the necessity of caution in 

 ascribing irregularities of seed shape in Peas to a failure of Mendelian dominance or 

 segregation ; and, as my own experiments show, there is little doubt that some at all 

 events of these irregularities are due to the various influences of the conditions of life, 

 rather than to heredity.) 



REFERENCES. 



Bateson, W., 1901. English translation of Mendel's original paper, with introduction. 

 Journ. Roy. Hort. Soc. xxvi. p. 1. 

 „ 1902. Mendel's Principles of Heredity (with portrait of Mendel, 

 bibliography and translations of Mendel's papers), xiv + 212 pp. 

 (Cambridge University Press.) 



