330 The Microscope. 



If we concisely review the facts, remedial practices may be sug- 

 gested. The destructive organisms infest any or all parts of the 

 plants and live over winter, either as spores or otherwise, in the old 

 material. In the case of bi'oom-corn, there is a large mass of this 

 old substance left upon the ground, and it has been observed that 

 since the improvement of plows permitting this refuse to be turned 

 under, the disease has been much more destructive than when it 

 was necessary to clear the ground by burning the old stalks. 

 Undoubtedly, one thing to do now is to return to the former prac- 

 tice, and carefully burn the stubble. But this does not dispose 

 of the old roots and underground parts of the stems, which are 

 infested with the parasites. Rotation of crops is better than 

 trusting to burning, and Held practice has given excellent 

 demonstration of the utility of this system of management. Crops 

 are sometimes injured on land not previously planted with sorghvun 

 or broom-corn; but the injury is invariably greater, so far as direct 

 observation has been made, when successive crops of these plants 

 are grown on the same land. The same microbe does not appear to 

 affect maize, wheat or oats, though it is probable that it does live 

 and prey on some other members of the great grass family. The 

 most serious damage is done to the roots, and, no doubt, these are 

 far more liable to be infected from organisms already in the soil than 

 from such as might be washed down into fresh ground by rains. If 

 the soil, on the other hand, contains great numbers of the living 

 microbes, many of these will get into the air by the evaporation of 

 water from the infested earth. This fact has been disputed, but 

 experiments have repeatedly shown that bacteria may be canied over 

 in the practice of distilling water, as well as disseminated in natu- 

 ral evaporation. Whether they ride on tiny droplets, or are simply 

 moved by the aerial currents produced, we need not stop to inquire. 

 Their own power of movement is of course useless for such dissem- 

 ination as we now consider. 



It is quite possible that special fertilizers may be of service in 

 checking the ravages of this disease, but nothing upon that subject 

 is known. There seems to be no difference in regard to the general 

 fertility of the soil. Indeed the more luxuriant the growth, the more 

 conspicuous the appearance of disease upon artificial infection. 

 Moist weather also seems favorable to the spread and abundant 

 development of the malady. Eains appear to be efficient agents in 

 the natural infections. During the unusual dry weather of the 

 present season the crops suffered little, comparatively, in the partic- 



