R. N. Sal A MAN 41 



Shape of Tuber. The tubers of etuberosum are, as already mentioned, 

 " round " — the seedlings comprise both " rounds " and " longs," and 

 amongst the latter are kidneys. The numbers are 18 round, 14 long. 

 It is evident that the " roundness " of etuberosum is of a quite different 

 order and with a different hereditary value to that of the domestic 

 varieties, and moreover, it is obvious that the " round " here is dominant 

 to the " long," whereas in the domestic types it was recessive. 



TIte Eyes. The eye of the parent tuber is " shallow " and very 

 insignificant. The seedlings can, as regards the tuber eye, be at once 

 divided into " deep " and " shallow." 



These are 26 "shallow " to 8 "deep." 



" Shallow " eye is therefore clearly dominant : in the domestic 

 variety it is as clearly recessive. 



The Colour of the Tuber. It will be remembered that, although the 

 etuberosum tuber is white, yet in 1908 certain tubers were noted to 

 have shown a slight purplish tinge. It is not therefore surprising to 

 find that the seedlings are varied in colour and that the parental white 

 is a dominant. 



The colours of the seedling tubers are white and deep purple. The 

 latter are identical in colour to those purple tubers dealt with in the 

 earlier part of this paper. 



The numbers of the different colourings are — 



White 13 



White tinged 12 



Deep purple (black) 13. 



The numbers suggest that purple is a recessive character and that 

 white is a simple dominant. In the domestic varieties the reverse is 

 true. No reds were formed. 



Crosses with Domestic Varieties. In 1906 I succeeded in effecting a 

 cross with " Queen of the Valley." Three seedlings only grew, and they 

 all died out. Mr Paton(7) crossed etuberosum by the white kidney 

 " Duchess of Cornwall," and he obtained 13 seedlings, the colour of 

 12 of which he describes, viz. 



9 white, 2 purple, 1 red, 



showing the dominance of white. It is of further interest to note that 

 he describes the shape of ten of them. Eight are " round " and two 

 are "long" (kidney and oval), again showing the dominance of the 

 etuberosum type of " roundness." 



