POTATO-ROT. 211 



was not made clear. Still others declared that it went in the air, 

 but without tlie slightest knowledge of the manner by which the air 

 becomes the vehicle for the transportation of contagion of an}- kind ; 

 and finally there were those who believed that it was a dispensation 

 of Divine Providence, sent upon the people as a punishment for 

 their sins. 



The True Cause. 



Immediately upon the outbreak of the potato-rot in Europe 

 investigations were made bj' careful scientific men, who discovered 

 that the diseased plants were more or less infected by an unmis- 

 takable fungus, the minute thread-like m3-celium of which pene- 

 trated in all directions through the tissues of the leaves, stems, 

 roots and tubes ; that through the stomats or breathing pores on the 

 underside of the leaves, the fruiting portions of the fungus extended 

 out into the air, and that through the corroding influence of the 

 mycelium the tissues were changed into the well-known condition 

 of the potatoes when attacked by the malad}'. 



Dr. Montague first described the fungus under the name of 

 Botryti's infestans. About the same time it was described bv 

 Madame Libert under tiie name of Botrytis devastalrix, and by M. 

 Desmazieres under the name of Botrytis fall ax ; but Dr. Montague's 

 name being the oldest in point of time is the one now adopted, but 

 in a revision of the genera this species has been placed in a new 

 genus and the fungus is now known by the name of Feronospora 

 infestans, Mont. 



For a long time it Avas hotl}' disputed that the fungus was the 

 cause of the potato rot. Some contended that it only lived in and 

 fed upon the fermenting and decomposing tissues of the potato, but 

 experiments conducted bj' DeBarj^ of Strasbnrg, and others, have 

 full}' estsblished the fact that this fungus is the real and true cause 

 of the potato-rot. Before we can hope to subdue an enemy it is 

 necessary to know its structure and habits, and then we ma}' pos- 

 sibly find some vulnerable point where it may be attacked with some 

 degree of success. 



Natural History of the Fungus. 



Like other fungi this species has a vegetating and a fruiting por- 

 tion which includes several kinds of seeds or spores as they are 

 called. The vegetating portion is represented by long slim branch- 



