Xcbmska Forest Fungi. II 



91 



or cup-shaped, membranous, coriaceous, carbonous, or sometimes 

 somewhat fleshy, usually black, sometimes bright colored. Ex- 

 ternally the members of the group resemble certain of the Sphac- 

 riaccons Ascomycctcs. 



Sphaeroidaceac: 



Here the pycnidia are globose, conic or lens-shaped, mem- 

 branous, carbonous, or somewhat coriaceous, black, immersed 

 or superficial, single or in a stroma. The conidia are 1- many- 

 celled, hyaline or dark. The following are some of the most 

 common members of the family. 



Phyllosticta. 



In this genus the black pycnidia are scattered about in small 

 sharply defined discolored spots on living leaves. The tissue in 

 the spots usually turns to a dull brown, or in some cases almost 



white, and is very clearly marked off 

 from the living tissue of the leaf. The 

 pycnidia are conspicuous as black specks 

 dotted over these discolored areas. 

 They usually originate beneath the 

 cuticle, and are thin-walled structures 

 with a nearly round pore above. See 

 fig. 16. The spores are ovate, oblong, 

 elliptical or globose, hyaline. The basi- 

 dia are either inconspicuous or none. 



Phyllosticta populina Sacc. 



Discolored spots angular, whiten- 

 ing out in drying with a dark colored 

 margin. Pycnidia dot-like, few to 

 rnyuosncta. man scattered over the discolored 



a. Habit upon the leaf. . .- <- n- i ..< 



b. Enlarged pycnidium. s P ts - Spores elliptical or oval, slightly 

 All highly magnified. olive-colored, 4-6x2-3 microns. Oc- 

 curs on the leaves of Populus deli aides 



as widely scattered spots that vary from 3-10 mm. in diameter. 

 See fig. 17 and 18. 



Phyllosticta scrotina Cook. 



Spots rusty-brown, circular, border darker. Pycnidia dark 

 brown, on the upper side of the leaf, scattered, dot-like. Spores 

 hyaline, elliptical-lanceolate, 12x4-5 microns. Common on 

 Pninns scrotina. 



Phyllosticta minutissima E. & E. 



Spots on both sides of the leaf, irregular in outline, 4-9 mm. 



