476 



Potato Leaf-Curl. 



[NOV., 



(Old Hoary or Taunton Buff), without the rough or felted chaff 

 which is being pushed forward for distribution as soon as 

 possible. 



A few years ago it was thought that the crossing of a 

 weak wheat on to a strong one would have produced progeny- 

 possessing an intermediate strength, and the most that could be 

 hoped for would have been an improvement worth having, but 

 of no great degree. Under those conditions, if a wheat could 

 not be found which would maintain a great strength in England 

 and by selection give a yield of wheat and straw satisfactory to 

 the grower, only indifferent results could have been obtained ; 

 to-day, as hybridising has been changed from a haphazard pro- 

 cess to a science, and as one or more wheats appear to have 

 been^found which will permanently maintain a great strength in 

 England, the Committee believe they will succeed in producing 

 strong wheats capable of giving high yields of grain and straw 

 as results of hybridising, even if selection fails. 



This disease (Macrosporium solani) is widely diffused. In 

 addition to Britain, it occurs on the Con- 

 Potato Leaf-Curl, tinent, and is rampant in the United States. 



It has occurred on Solanam Commer- 

 soni, grown at Kew. 



The curling of the leaves is usually the first indication of 

 the presence of the fungus, although the base of the haulm is 

 the portion first infected, and the curling of the leaves is due to 

 the ascent of water and food being checked by the upward 

 growth of the fungus mycelium in the tissues of the haulm. 

 As the mycelium increases in quantity in the tissues, the haulm 

 becomes limp and collapses owing to lack of water. 



At a later stage, the fungus breaks through the tissues to 

 produce its fruit, which is indicated by the presence of numerous 

 irregular, blackish, minutely velvety patches scattered over the 

 surface of the haulm and leaves. 



— It has been found that in some instances the mycelium of 

 the fungus passes down the haulm into the tuber. In such cases, 

 the mycelium in the infected tuber passes into the sprout and 



