CONTEIBUTIONS FROM THE WISLEY LABORATORY, 



41 



samples of seed potatos obtained from local merchants yielded the 

 following proportions of affected tubers : — 



Variety Proportion of affected tubers 



'Early Eegent ' 1/75 



' Duchess of Cornwall ' . . . . 0/70 



' Schoolmaster ' 30/140 



' Edina ' 40/154 



' Scotch Express ' 6/140 



' Snowdrop 3/86 

 'Up-to-Date' ... . . . 1/100 



' Table Talk ' 3/100 



From this table it can be seen that a very high percentage of 

 two of these varieties was diseased, although a fair price for small 

 quantities of good ' sets ' had been paid. It is important to note that 

 if potatos from the same source had been sold for domestic purposes, 

 at the price which sound ones should command, the consumer would 

 have experienced considerable loss. 



In January 1909 I received 1 cwt. of potatos from Berkshire for 

 experimental purposes in connexion with internal disease, and about the 

 same time 1 cwt. of diseased potatos of the variety ' British Queen ' 

 from a farm in the county of Durham. The tubers of both consign- 

 ments were very badly blackened, in addition to other diseases 

 present. The blackening, however, w^as not confined to potatos other- 

 wise diseased. In these instances the general symptoms were different 

 from those hitherto observed in that the black areas were less definitely 

 localized, but were distributed generally throughout the whole tuber 

 (figs. 20 G and 21). In 1910 and again in 1911 examples were forth- 

 coming of potatos affected in the manner first described, from different 

 sources, during the storage season. 



Bruise appeared in several varieties examined in 1912. The 

 * Factor,' grown near Wisley, was slightly affected. * Northern Star,' 

 sent by Mr. W. G. McGowan from East Lothian, in connexion with 

 other experiments, was also affected, though somewhat differently from 

 those in all the cases cited above. The matter was complicated in this 

 case by the presence of streak-disease also. 



The last examples of typical bruise were received from Professor 

 Etienne Foex, of Montpellier, in April. The tubers originally came 

 from the Departement des Hautes Alpes, and were sent to Montpellier 

 by Professor Cadoret, with the note that the disease — presumably the 

 one affecting the tubers sent to me — is said to occur throughout the 

 Department, that it was worse in 1910 than in 1911 (a very dry 

 year), and that the variety * Early Eose ' was more affected by it than 

 the local varieties were. 



With a view to ascertaining whether this disease would occur in 

 the produce obtained from planting diseased tubers, small experiments 

 were arranged in 1908. 



