PHYCOMYCETES. 



MUCORACE.E. 



RHIZOPUS NIGRICANS, Ehr. 

 (Soft Rot of Sweet Potato). 



A disease of the tubers of the sweet potato has been 

 reported to be caused by this fungus in New Jersey. 



The disease is sometimes met with in the field, but is 

 much more frequent among stored potatoes. When attacked, 

 the potatoes become soft and are worthless. In the 

 storehouse the disease spreads rapidly from infected to 

 healthy tubers. 



The fungus effects an entrance at a wound on the tuber 

 and develops especially after the tuber has been stored. It 

 makes its appearance on the diseased parts in the form of 

 a black mould. 



The following remedial measures have been recom- 

 mended : — 



The storing of the tubers in a well-ventilated room at a 

 temperature of yo° or more. 



Careful examination at repeated intervals for any soft 

 potatoes and their immediate removal from the storehouse. 



Diagnosis: — Sporangiferous hyphae erect, in fascicles of 

 3-10, springing from stoloniferous hyphae which give off 

 rhizoids at corresponding points; sporangia globose,bhckish- 

 olive, granular, 100-300 microns diamr. ; columella hemis- 

 pherical ; spores broadly elliptical or globose, grey, variable 

 in size, 8-14 microns diamr. ; zygospore subglobose or tun- 

 shaped, 150-200 microns ; epispore brown with rounded 

 warts. 



HALSTED : Some fungus diseases of the sweet potato " ; 

 New Jersey, Agric. College Exp. Station, Bull. j6, Nov. 

 28, 1890. 



Peronosporace^e. 



PHYTOPHTHORA OMNIVORA De Bary. 

 (Black Rot of Cacao Pods). 



The disease has within recent years become much more 

 general and destructive to pods of the cacao plant in 

 Trinidad. In addition to occurring in the West Indies the 



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