34 Genetic Studies in Potatoes 



will yield " uprights " and " prostrates " in the ratio of 15 : 1, about one- 

 third {^) should give 63 : 1 and the remainder (i^-g) 3 : 1. 



In Table VI not only is segregation seen to take place but it is 

 evident that different impure "upright" individuals give rise to different 



TABLE VI. 



Serial No. Name of Family Where Grown Method of Pollination Upright 



123 B, 2,16 Fb 165 xER&oxM5B 35, 1,2,1& Barley By hand. Protected 



12BB, 16, 32 „ X „ 16, 32 



123 B, 24, 19 „ , X „ 24, 19 



,, 23 ,, X ,, J) 23 



65 X 65 



127 B, 2,32 J2xjRJRll, 40, 48x3/5 5 35, 28,2, 32 

 34 „ X „ ,, 34 



families of "uprights" and "prostrates" bearing ratios at least as diverse 

 as 3 : 1, 15 : 1 and 63 : 1. The numbers both of the families grown and 

 that of plants which compose them are too small to determine accurately 

 the rather complex relations of the " prostrate " family. 



In view of the very small proportion of " prostrates " which occur 

 larger F2 and F3 families are required, but the results at present point 

 to the conclusion that at least three factors are at work. In view of 

 this the discovery of but one original recessive " prostrate " plant in one 

 family among many hundreds involving the examination of about fifty 

 thousand seedlings is not surprising. 



As to the intermediate type we have already referred to ihe " pro- 

 cumbent," besides which there are many plants which though counted 

 amongst the " uprights " because they neither crept nor were deficient 

 in interfascicular wood yet differed from the fully "upright" plant, some 

 tending to fall to the ground at an early age whilst others grew in a 

 bush-like manner. There are certainly many intermediate stages 

 between the true "upright" and the true "prostrate" besides the 

 "procumbent," but there are not sufficient criteria to justify us in 

 making a more critical classification. 



The Procumbent Variety. 



It has already been mentioned that an intermediate form has been 

 found in our cultures forming a link between the " upright " and the 

 " prostrate " varieties. This type was recognized as an abnormal one 

 in 1910 and photographed in 1911, but its true significance was not re- 

 cognized till 1912 when in a family (/2 x i^i^ll, 40) in which the Congo, 

 Flourball and Reading Russet varieties take part, a certain proportion of 



