28 



Genetic Sttidies in Potatoes 



The three exceptions occurred in two families both arising from berries 

 which set naturally. In the first case Mb £35, 1 a single very vigorous 

 plant occurred with a " procumbent " habit of growth, one of the main 

 stems especially turning upwards so as to render it quite distinct from 

 the adjacent " prostrate " plants (Plate II, fig. 4). The stem of this, 



however, proved to be structurally of the "prostrate" type. The two 

 further exceptions occurred in one of the families grown from one of the 

 naturally fertilized berries of M5 BSo, 28. The stems were not of the 

 " prostrate " variety ; some of them bore tubers which did not conform to 

 the family type, and there is very little doubt that these abnormal 

 plants are due to foreign insect-borne pollen. We may safely conclude 

 that the new variety breeds true. In 1913 three seedlings, offspring of 

 one of the original family, produced four berries by natural and one by 

 hand pollination under protection. The results from three of the families 

 are anomalous as shown in Table II, biit from unmistakable evidence 

 deduced from the characters of the flowers, stolons and tubers we were 

 able to show that the parent plant had been fertilized by a derivative 

 of S. edinense which was growing near by and whose habit is " upright." 

 The fact that in three of the families " prostrates " as well as " uprights " 

 occur implies that besides the foreign dominant " upright " pollen the 

 flower had been to some extent self-fertilized. 



