596 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



in damaging the foliage of potato plants or causing its ultimate disease 

 and death. Experiments were at once commenced at the Physic 

 Garden, Chelsea, and have since been continued at Wisley, but a 

 description of these particular experiments and the results obtained 

 must form the subject-matter of a separate communication. This 

 Report deals entirely with experiments with tubers. 



A. — Experiments in the Garden. 



Planting sound tubers of suitable " seed " size (whole sets). 



Season 1912. — It was deemed advisable first of all to try the 

 effect of planting a plot of ' President ' at Wisley in order to see 

 how the plants produced compared with those grown on the plots at 

 Chelsea and Wye in 191 1. Accordingly 1 cwt. of ' President ' was 

 purchased from a potato merchant, who stated that they had been 

 raised at Dunbar in 191 1. These potatos were planted in light sandy 

 soil at Wisley after it had been treated with a little artificial manure. 



The result obtained was much worse than that experienced at 

 Chelsea and Wye, and quite as bad as the more serious cases observed 

 in Scotland in 1910. The pathological condition became evident in 

 a large proportion of plants before flowering time. These plants 

 were dwarfed and had folded and blotched leaves, often tinged 

 with a yellowish or pinkish colour just as in the case of the Scots 

 plants (figs. 190, 191, 195, 196). At Wisley, although the plants 

 flowered (both good and bad) , very few set seed, whereas in Scotland 

 a large proportion (both good and bad) formed seed bolls. 



The condition of the plot in August is shown in the plan on the 

 opposite page, which represents every plant grown and its actual 

 position. 



Upon lifting, the produce from the blotched plants proved to be 

 extremely small. Each plant produced two or three small tubers 

 similar to those shown in the photograph of tubers from bad plants 

 grown at Wye (fig. 193). The crop as a whole was poor and of little 

 value. 



Season 1913. — Tubers from the 1912 crop were saved and planted 

 again at Wisley in 191 3, near the site of last season's plot, and a pre- 

 cisely similar result was obtained. On October 10, when the tubers 

 were lifted, the foliage of a few blotched plants was still standing. 

 These plants were lifted and bore two or three small tubers each. 

 The foliage of the more healthy plants had died down, and at these 

 places the tubers were more numerous and larger, but the yield on the 

 whole was very poor. 



B. — Variability in Tuber Characters. 



By special request a grower in Scotland selected about 200 tubers 

 that he judged to be suitable for " seed " from the 1911 crop of 

 'President,' and forwarded them to Wisley for experimental purposes. 

 On January 15, 1912, the writer re-selected 51 of the very best of the 

 grower's choice and very carefully examined each tuber. The number 



