Principles of Heredity 151 



the second hybrid generation dimorphic as usual. The 

 wrinkled peas were selected and sown and gave wrinkled 

 peas and round peas, becoming "true" to the wrinkled 

 character in one case only in the fifth year, while in the 

 second case that of a Telephone cross there was a mixture 

 of round and wrinkled similarly resulting from wrinkled 

 seed for two years, but the experiment was not continued. 



These at first sight look like genuine exceptions. In 

 reality, however, they are capable of a simple explanation. It 

 must be remembered that Rimpau was working in ignorance 

 of Mendel's results, was not testing any rule, and was not 

 on the look out for irregularities. Now all who have 

 crossed wrinkled and round peas on even a moderate scale 

 will have met with the fact that there is frequently some 

 wrinkling in the cross-bred seeds. Though round when com- 

 pared with the true wrinkled, these are often somewhat more 

 wrinkled than the round type, and in irregular degrees. 

 For my own part I fully anticipate that we may find rare 

 cases of complete blending in this respect though I do not 

 as yet know one. 



Rimpau gives a photograph of eight peas (Fig. 146) 

 which he says represent the wrinkled form derived from 

 this cross. It is evident that these are not from one pod 

 but a miscellaneous selection. On close inspection it will 

 be seen that while the remainder are shown with their 

 cotyledon-surf &ces upwards, the two peas at the lower end 

 of the row are represented with their 7^7r-surfaces 

 upwards. Remembering this it will be recognized that 

 these two lower peas are in fact not fully wrinkled peas 

 but almost certainly round " hybrids," and the depression 

 is merely that which is often seen in round peas (such as 

 FUlbasket\ squared by mutual pressure. Such peas, when 

 sown, might of course give some round. 



