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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



(gravel, grit, and coarse sand) which ensure porosity and consequently 

 warmth, nor in the finest materials (fine silt and * klay ') which secure 

 retention of water and fm'ther, that " although a light soil of good 

 physical composition (e.g. Thornton Loch) produces the best quality 

 tubers in a moist climate, a heavy soil may do better in a warm dry 

 climate. It is noteworthy that bruise has been frequently found in 

 potatos attacked by wireworm on land only a short time brought into 

 cultivation. In cases of this kind it is highly probable that the soil 

 still requires a considerable amount of attention, and the treatment 

 it receives ■ should be considered relatively to the climatic conditions 

 which obtain in particular districts. 



The aim of the writer in this paper is merely to sort out and 

 describe a form of disease which has hitherto been confused with others ; 

 a great deal more work on the, subject remains to be done — notably (a) 

 the study of a possible connexion between bruise and the phenomenon 

 investigated by Ashby (blackening after cooking) ; and (b) a more 

 detailed investigation of the occurrence of solanin in the potato. 



The writer desires to express his thanks to Mr. F. J. Chittenden, 

 F.L.S., for his advice and criticism. 



Description of Figures. 



Figure 20. — a. Typical example of bruise in a tuber of an unknown variety 

 obtained from Devonshire in 1908. The mottled appearance on the 

 right is the expression of the interwoven diseased and healthy cells. 

 The vascular bundles are not discoloured. 



B. Another example of bruise. The diseased area occurs on both sides o^ 

 the ring of principal bundles which are not discoloured. The cleari 

 bundle area can be distinguished in the middle of the discoloured 

 tissue. 



c. Tuber of the variety 'British Queen/ with blackened flesh. 



Figure 21. — a.-f. Examples of tubers of the varieties ' British Queen ' and 

 ' Sutton Flourball/ with blackened flesh. These form a series in the 

 extension of the disease from the neighbourhood of the vascular 

 bundles inwards. 



