384 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Tablk II.— {continued). 

 Variety. Remarks. 



3. Aberlady Early . . . ) Grown near Edinburgh ; slightly affected ; artificial 

 Up-to-Date . . . . i manure and dung used. 



[Grown at Auchnagatt, Aberdeenshire ; slightly j 



4. Langworthy . . .1 diseased ; soil loamy ; six to ten years' rotation i 



^ or longer. 



The case at Prestonpans appears to be similar to that already I 

 described at Cleadon. It seems improbable that the disease was intro-L 

 duced by the seed obtained from so many different localities. 



- Amongst the varieties grown at Cleadon, * King Edward VII. ' 

 and * Midlothian Early ' were more badly diseased than the others. 

 An attempt was made, therefore, to find out whether the former variety 

 was affected to the same extent in other districts. The result of these, 

 observations is shown in the following table: — 



Table III. 



Canker in the Vakiety ' King Edward VII.,' September 1910. 



District 



1. Farm at Hawthornden, 



near Edinburgh 



2. Farm at Hawthornden 

 8. Experimental station, 



Edinburgh district. 



4. Prestonpans 



5. Garden at^ Armstrong Col- 



lege 



6. Cleadon — same seed used 



as in 5 



7. Cleadon — another field 



8. Allotment garden,Gosforth, 



Newcastle-upon-Tyne 



9. Auchnagatt, Aberdeenshire 



From this table it is clear that a variety which in one district i.'| 

 badly diseased, may be only slightly affected in another; and some-i 

 times does not take the disease at all, or only slightly, when otlieii 

 varieties on the same farm are affected. j 



The first crop at Cleadon in 1909 was grown in a field bordering 

 those used in 1910, and in this year the potatos were badly affectecj 

 with Phytophthora ; but although the farm was visited repeatedl};! 

 (luring the season and a large number of tubers was examined, not i, 

 single case of canker was observed. If the disease had affected th(j 

 crop to any extent it could hardly have been overlooked. Fortunately 

 several of the diseased tubers — typical examples grown in 1909— j 

 were photographed. The potatos in the photographs (figs. 103 a, b, d, Ej 

 show only a few scabby spots, possibly caused by Spovgos'pora. Tliesj 

 should be compared with fig. 103 f, which represents a tuber grow n ii| 

 1910 showing similar scabby spots, known to be caused by ^pon^ffj 

 spom. It seems, therefore, that potato canker was either not presen; 

 in the soil of the field used in 1909 or, more probably, was present 

 but had not manifested itself to a recognizable extent. Cases of ; 



Observations 



Not affected, but disease 

 present in other varieties 



Slightly affected 



Not affected, but disease 

 present in other varieties 



Slightly affected 



Not affected 



Badly affected 



Badly affected 

 Badly affected 



Not affected 



Manure 



From gum works. 



From gum works. 

 Sulphate of ammonia 



and dung. 

 Partly artificial. 

 A little artificial. 



Peat-moss litter anc 



farmyard manure 

 Similar to 6. 



A local potato manur 

 and dung. 



