MUCOR. 207 



Berkeley, and later DeBary has given this fungus attention. The rapid 

 decay of both foliage and tubers is a good character, accompanied by a 

 very- offensive odor, which is easily recognized by all who have once 

 experienced it. The condition most favorable for the growth of this 

 fungus is a moisl and sultry atmosphere of a temperature of 70° Fahren- 

 heit. The manner in which the germ tube of the conidia spores enter, 

 the leaf is interesting. 



The name "downy mildew " has been given to this fungus, since 

 under favorable circumstances a downy or mould-like growth forms 

 itself on the under surface of the leaf. Thus far the upper surface does 

 not show any signs of the disease. This downy surface are the conidia 

 spores with the hymenium threads. These conidia spores are light and 

 may be carried long distances by the wind. It is largely owing to these 

 spores that it is so infectious. After a time the top part of the leaf 

 changes color, from a yellowish to dark brown or even black. 



After these summer spores mature on the leaf, some fall on the ground 

 and are brought in contact with the tuber, where they germinate and 

 enter the substance of the potato, there to produce the same bad effect it 

 had on the leaf and stalk. It is through the mycelium remaining in the 

 potato that the fungus is carried through the winter. 



As for a preventive, the best thing to do is to use some poisonous 

 spraying mixture. Since Paris green is used so freely to destroy the 

 potato bug, we have no trouble with this fungus. Paris green answers 

 the double purpose of killing the potato bug and the Phytophora infestans. 



Genus IV. MUCOR. Moulds. 



Threads free, sporangia at length bursting. Zygospores 

 present, developed on the mycelium. 



M. phycomyces. Berk. 

 Mycelium obsolete, olivaceous, shining ; sporidia yellowish. 



To get specimens of this species, the best place is on old greasy cellar 

 walls. 



M. mucedo. L. Common Mould. 

 Byssoid, sporangia and sporidia globose, at length blackish. 



