Il6 MINNESOTA BOTANICAL STUDIES. 



Order Phacidiales. 

 Family VI. Phacideaceae. 



Mycelium within the substratum ; saprophytic and parasitic ; cups 

 immersed or superficial, membrane covering hymenium until matu- 

 rity of the spores, ruptures irregularly, more or less coriaceous, 

 black. 



I. RHYTISMA FR. 



Cups crowded on a thin, broadly effused, black, crust-like stroma ; 

 elongated finally gaping and exposing the pale disc ; spores elongate, 

 slender, hyaline, continuous, arranged in a parallel fascicle m the 

 ascus. Species commence as parasites on living leaves forming 

 pitch, black patches and bearing conidia during the autumn and 

 winter. The following spring when the leaves are partially decayed 

 the ascophores or cups are born. 



I. Rhytisma salicinum (Pers.) Fries, Vetensk. Akad. Handl. 104. 

 1819. (Plate XIX. Fig. 2.) 



Xyloiiia salicinum Pers. Disp. Meth. Fung. 5. tab. 2. f. 4. 1797. 



Stroma forming raised, circular or irregular thick, shining-black 

 patches on the upper surface of the leaves; to i cm. in diameter; in- 

 terior white ; ascophore roundish or oblong ; spores needle-shaped, 

 acute, curved, continuous, hyaline, guttulate, 60-90x1.5-3 mic. ; 

 paraphyses filiform, slender, apex wavy, hyaline or tinged brown. 



On upper surface of various species of SaJix leaves, very abun- 

 dant. Winona, Aug. 1888, Holzinger; Hennepin, June 1890, Sheldon 

 4242; Cass, Aug. 1890, jNIacAIillan 90; Crow Wing. Aug. 1890, 

 MacMillan & Sheldon '/t^,22; Brown, July 1891, Sheldon 714, 846; 

 Pope, July 1891, Taylor 856, Mac^^Iillan 4; Brown, July 1891, 

 Sheldon 1077; Traverse, Sept. 1893. Sheldon 7248; Lake, Aug. 1903, 

 Freeman & Ballard 185 ; Cook, Aug. 1903. Freeman & Ballard 59. 



Exsiccati : Thiimen, Fungi Austr. 186, 185; Thiimen, Mycoth. 

 univ. 1664; Sydow, Mycoth. March. 1652, 3055 ; Krieger, Fungi Sax. 

 35; Ellis & Everhart, North American Fungi. 190. Plates: Tulasne^ 

 Sel. Fung. Carp. 3. tab. 15. fig. 13-22. 



