137 



possesses no inconsiderable value, when the large 

 acreage of the crop grown is taken into consideration, 

 or is he to burn it and lose this value ? If he follows 

 the dictates of the majority of scientific investigators 

 he will be foolish enough to risk the chance of their 

 being right, and will not destroy the haulm, but use it. 

 If he distrusts them he will be foolish enough to burn 

 the haulm and lose the value it possesses. While the 

 matter is in its present state it is correct to follow M. 

 de Bary in believing that the disease is only propagated 

 by means of the dormant mycelium, but it is safer to 

 distrust it so far as to destroy the haulm. According 

 to M. de Bary, the mycelium assumes activity when 

 the temperature is favourable, and ramifies through 

 the plant as it grows. If circumstances are favourable 

 the mycelium bursts through the leaves and the aerial 

 hyphse bearing the spore cases are produced. Mr. 

 Smith says that the leaves are struck from the outside, 

 and when the spores germinate they find their way 

 into the plant and ramify to all parts. 



The Spread of Disease. 



The manner in which the disease is carried from plant 

 to plant is fortunately proved satisfactorily. The 

 conidia, or spores, are carried on the aerial hyphaa 

 or branches of the fungus growing outside the leaf. 

 The branches are jointed somewhat like a bamboo 

 cane, and a conidium is given off at each joint. These 

 contain a thick liquid substance which, when the 

 conidia ripen and are placed in moisture, breaks up 



