49 



LI I. W. A. Roach. "Studies in the Varietal Immunity of 

 Potatoes to Wart Disease (Synchytrium Endobioticum 

 ScHiLB., Perc.)/' Part I. — The Influence of the 

 Foliage on the Tuber as shown by Grafting. Annals 

 of Applied Biology, 1923. Vol. X. pp. 142-146. 



(irafting experiments of a preliminary nature have been carried 

 out to throw light on the functions of the various organs of the 

 potato plant in rendering the tubers immune or susceptible to 

 Wart Disease (Synchytrium endobioticum Schilb., Perc). 



Composite plants were built up by grafting in the following 

 ways : — 



3 plants of the type Immune grafted on Immune 



3 ,, ,, Susceptible ,, ,, 



4 ,, ,, Immune ,, Susceptible 

 2 ,, ,, Susceptible ,, ,, 



The results indicate that the character of the foliage has no 

 influence on the immunity or the susceptibility of tubers to Wart 

 Disease. 



It follows that no comi:)ound synthetised in the leaves is likely 

 to be responsible for separating potatoes into "immunes" and 

 "susceptibles." The inxestigation is being continued with the 

 view of finding, if possible, the chemical differences corresponding 

 with the biological differences between immune and susceptible 

 varieties. 



TECHNICAL PAPERS. 



CROPS AND CROP PRODUCTION. 



LIII. E. J. RussKLL. "The Barley Crop. A Study in Modern 

 Agricultural Chemistry." Journal Inst. Brewing, 

 1922. Vol. XXVIII. pp. (i97-7l7. 



Barley, like wheat, flourishes best in relatively dry conditions, 

 and the map showing its distribution in England and Wales is 

 much like an inversion of the rainfall map. In Norfolk it occupies 

 no less than 15% of the land in cultivation and in other counties of 

 low rainfall it occupies between 9% and 14% ; in the wetter 

 counties, however, it occupies much less. The yield is chiefly 

 determined by the quantity of nitrogen supplied. When barley is 

 grown year after year on the same ground at Rothamsted the 

 yield steadily falls off for some reason which cannot yet be found. 

 This falling off is less with farmyard manure than with artificial 

 fertilisers. In ordinary farm practice there is no indication of 

 falling yields, but rather the contrary; given adequate manuring, 

 however, the yield is still limited by the season and the strength 

 of the straw. 



It is often stated that the quality or malting value of the barley 

 is inversely related to the nitrogen content of the grain, and where 

 large differences are concerned this is generally true. But on any 

 given farm it does not appear that the nitrogen content is much 

 affected by the manuring so long as the conditions are not pro- 

 foundly altered ; the valuation also is not influenced in any regular 

 way. 



