200 SPH.5i;RIACE^. 



Genus VAI,SA. 



Perithecia carbonaceous, perfect, circinating, elongated into 

 converging necks ; ostiola erurapent, jointed together or ending 

 in a common disk. 



V. Americana. 



This is a conimon fungus on cordwood with the Vjark on. 



Genus X. SPHERIA. Hall. 



Perithecia black, carbonaceous pierced at the apex, mostly 

 papillate, superficial or erumpent, without any stroma ; sporidia 

 simple or septate, hyaline, or colored, variable. — Cooke' s British 

 Fungi. 



S. morbosa. Schw. Plum Knot. 



This fungus, according to the new nomenclature, is named 

 Plowwrightea morbosa. 



Perithecia, black, carbonaceous ; asci with eight sporidia, 

 paraphysis accompanies the asci. Spermogonia are also 

 present. 



Conidia or summer spores are early and abundant. They appear as 

 soon as the warm rains of June arrive, when you can find them on the 

 different species of the plum and red sour cherry trees. The mycelium 

 enlargement on the bark soon ruptures, when at the same time the 

 hyphse, bearing conidia spores, appear, giving the surface an olive- 

 green velvety appearance. 



It is by means of these conidia spores that this fungus is so contagious. 

 They ripen and are carried by insects and wind to new host trees, where 

 under favorable conditions they form new fungal growths, and the fungus 

 is spread indefinitely from tree to tree, from neighbor to neighbor. 



The perithecia, with the asci, are found later after the conidia have 

 done their work. They are the winter spores and do not ripen until 

 February and March. It is wonderful how nicely these spore cases 

 (perithecia) are imbedded in a hard crust for their winter quarters. 



This fungus is perennial, and having once gained a home in a twig 

 will soon spread by new knots forming continually. 



