CONTRIBUTIONS FROM THE WISLEY LABORATORY. 6ll 



Exp. III. Rows of each of the following varieties were planted 

 adjoining the plot used for the ' Duke of York ' : 



(a) ' Sutton Flourball.' — Disease-free sets were selected from 

 potatos raised at Walton-on-Thames, in soil that had produced crops 

 affected with internal disease, in 191 1. 



(b) ' Langworthy,' ' Up-to-Date,' and 1 Northern Star.' — Disease- 

 free sets were selected from tubers raised, in 191 1, on land that had 

 produced crops affected with streak. 



(c) ' Langworthy.' — Disease-free sets were chosen from a sample 

 sent to the Director from Liverpool in 1912. 



The tubers were lifted at the end of August. Those examined 

 yielded the result shown in the following Table. 



Table V. — Experiment with other Varieties in 1912. 





Number 

 of tubers 

 examined 



Streak 



Blotch 



Other 

 marks 



Phyto- 

 phthora 



' Sutton Flourball ' 



341 



O 



9 



O 



13 



1 Langworthy ' . 



IOO 



O 



2 



I 



O 



< Up-to-Date ' . 

 ' Northern Star ' 



IOO 



O 



0 



I 



8 



IOO 



O 



0 



O 



0 



4 Langworthy ' (Liverpool) ' . 



200 



8 



6 



15 



3 



The cases among ' Sutton Flourball ' were exceedingly slight, 

 the flesh being slightly spotted in each case. There were eight 

 pronounced cases of streak and six definite cases of blotch among 

 the ' Langworthys ' from Liverpool ; in the fifteen undefined cases 

 the flesh appeared semi-transparent and tinged with brown in places. 



Experiments in 1913. 



Disease-free tubers from the 1912 crop were selected for planting 

 in 191 3 on land adjoining that used in the previous year and not 

 before planted with potatos. About sixty sets (half-tuber) were 

 chosen from the produce yielded in each of the lots A, C, B, D, E, 

 and F in the previous year — all of ' Duke of York.' In addition to 

 these about sixty sets of ' Duke of York,' affected with streak, 

 were selected from the diseased tubers produced in the 1912 crop 

 (lot G). Lastly, three rows of tubers selected from the produce of 

 each of the other varieties used in 191 2 were planted (lots H, I, 

 J, K, L). 



The sets were planted about the middle of April, and the produce 

 lifted on October 10. The yield was, on the whole, very poor 

 and very uneven, as is usual when an attempt is made to grow 

 potatos from seed raised in the garden. The tubers were examined 

 during October and the results obtained are shown in the following 

 Table. 



2 s 2 



