Principles of Heredity 119 



III. THE FACTS IN REGARD TO DOMINANCE OF 

 CHARACTERS IN PEAS. 



Professor Weldon refers to no experiments of his own 

 and presumably has made none. Had he done so he would 

 have learnt many things about dominance in peas, whether 

 of the yellow cotyledon-colour or of the round form, that 

 might have pointed him to caution. 



In the year 1900 Messrs Vilmorin-Andrieux & Co. were 

 kind enough to send to the Cambridge Botanic Garden on 

 my behalf a set of samples of the varieties of Pisum and 

 Phaseolus, an exhibit of which had greatly interested me 

 at the Paris Exhibition of that year. In the past summer 

 I grew a number of these and made some preliminary 

 cross-fertilizations among them (about 80 being available 

 for these deductions) with a view to a future study of 

 certain problems, Mendelian and others. In this work 

 I had the benefit of the assistance of Miss Killby of 

 Newnham College. Her cultivations and crosses were 

 made independently of my own, but our results are almost 

 identical. The experience showed me, what a naturalist 

 would expect and practical men know already, that a great 

 deal turns on the variety used ; that some varieties are 

 very sensitive to conditions while others maintain their 

 type sturdily ; that in using certain varieties Mendel's 

 experience as to dominance is regularly fulfilled, while in 

 the case of other varieties irregularities and even some 

 contradictions occur. That the dominance of yellow 

 cotyledon-colour over green, and the dominance of the 

 smooth form over the wrinkled, is a general truth for 

 Pisum sativum appears at once ; that it is a universal 

 truth I cannot believe any competent naturalist would 

 imagine, still less assert. Mendel certainly never did. 



