WHITE— STUDIES OF INHERITANCE IN PISUM. 571 



Tschermak, Lock and Bateson have made many crosses involv- 

 ing these characters but the actual numbers are given in only a few 

 cases. Bateson (i) and Lock (54, 56) both obtained intermediates 

 in some crosses. 



In F3, from seed of 100 parchmented Fo plants, Mendel found 

 29 that bred true and 71 that had both parchmented and non-parch- 

 mented offspring. The non-parchmented Fa's always bred true. 

 In F^, no exceptional results were obtained. 



Mendel, Lock and Tschermak have always found parchmented 

 pods to be inflated and non-parchmented to be constricted. 



N on-parchmented X non-parchmented in some cases give only 

 non-parchmented in F^. In other cases (Vilmorin 89) in a large 

 series of crosses between diverse varieties of non-parchmented peas, 

 the Fi progeny have been frequently parchmented. In Fo these 

 parchmented F/s have produced approximately 9 parchmented : 7 

 non-parchmented progeny. 



Interpretation. 



Parchmented varieties of peas may be regarded as dift'ering from 

 those having non-parchmented pods by the presence of either one 

 or two factors (P and V). No varieties or tested out segregates 

 have been recorded representing the absence of both P and V, but 

 from Vilmorin's results one should expect to find them. All parch- 

 mented varieties may be regarded as PPVV, while non-parch- 

 mented varieties so far investigated are either PPvv or ppVV. 

 PPvv X ppVV would give parchmented F^'s and 9 parchmented : 7 

 non-parchmented in F,, while either PPw or ppVV X PPVV 

 would give parchmented F/s and a 3 : i ratio in Fo. 



19. Adherence between Mature Peas in the Pod. 



As well known, all varieties of peas except one have pods in 

 which the seeds are entirely free from each other. This one ex- 

 ceptional variety known as " Chenille " has pods with free imma- 

 ture seeds, which when mature adhere more or less closely to each 

 other as though stuck together with glue, and this particular char- 



