88 Forest Club Annual 



Uncinula circinata C. & P. 



This species is confined mostly to the lower sides of the 

 leaves. The mycelium is evanescent, or persistent in definite 

 spots. The perithecia are usually scattered. Appendages densely 

 crowded, tip coiled. This is the common mildew on Acer sac- 

 charinum. 



Uncinula salicis (DC.) Wint. 



This species is found very commonly on species of SalLv. 

 It differs little from the above species. The common hosts are : 

 Sali.v amygdaloidcs, S. cordata, S. fluviatalis, S. humulis, S. sp. 

 and Popnlus dcltoidcs. 



Sphacriaceac: 



This family of black fungi is characterized by the presence 

 of brown or black perithecia that are typically globoid, often with 

 a beaked ostiole. The perithecia are simple, clustered or imbedded 

 in a stroma ; they are membranous, coriaceous, or carbonous, and 

 they dehisce by a round pore or ostiole. When the perithecia 

 are imbedded in a stroma each perithecium is distinct from the 

 substance of the stroma, not a mere locule in the stroma. The 

 mycelium is scanty and immersed after the perithecia are formed, 

 rarely persisting in the form of a subiculum. Many species in the 

 family produce, especially in their conidial stages, very destruct- 

 ive plant diseases. 



Sphaerella 



The perithecia in this genus are thin-membranous, globose- 

 lenticular, and are covered by the epidermis of the host or soon 

 erumpent. The ostiole is usually short papillate. The asci are 

 8-spored, and are accompanied by paraphyses. The spores are 

 elliptical or oblong, 2-celled and hyaline, or slightly colored. 



Sphaerella nigrita Cook. 



Perithecia somewhat immersed on the lower side of the leaf 

 in orbicular discolored spots. Asci clavate, spores elongate-ellipt- 

 ical, uniseptate, hyaline, 15-4 microns. On fallen leaves of 

 Quercus macrocarpa. The more or less irregular orbicular spots 

 with their clusters of perithecia on the under side of the leaves 

 are from 3-6 mm. in diameter and give an appearance of sooty 

 blotches scattered over the affected leaf. 



Dothideaceae: 



A stroma is typically produced in this family, in which the 

 perithecia are more or less completely sunken and reduced to 

 locules, that is, there is not the definite black perithecial wall 



