Phylum Inophyta [ 133 



The more familiar Perisporiacea are those of family Erysiphea [Erysipheae] 

 Winter. They are parasites on plants, mostly producing a white mycelium on the 

 surface and sending brief haustoria into the epidermal cells. They produce abundant 

 conidia in erect unbranched chains; this habit explains the common name of powdery 

 mildews. Harper's important studies of the morphology of Ascomycetes were in large 

 part made on powdery mildews. The gametes are uninucleate and unite directly, the 

 egg bearing no trichogyne; the ascogenous hyphae are brief; each minute black 

 globular cleistothecium bears an equatorial whorl of appendages of a form charac- 

 teristic of the genus. In Erysiphe and Sphaerotheca iS. pannosa is the common rose 

 mildew), the fruits bear unbranched sinuous appendages like vegetative hyphae; the 

 fruit of Erysiphe contains several asci, while that of Sphaerotheca contains one. In 

 Microsphaera {M. Alni is the powdery mildew of lilac) and Podosphaera, the ap- 

 pendages are dichotomously forked near the tip; the fruit of Microsphaera contains 

 several asci, that of Podosphaera only one. The appendages of Uncinula are hooked 

 at the tip. Those of Phyllactinia are like sharp spikes with bulbous bases. 



Other Perisporiacea, parasitic or saprophytic on plant material, are compara- 

 tively poorly known. The fruits may bear appendages of other characters than those 

 of the Erysiphea, or none, and may be characteristically clustered or borne in 

 stromata. In some examples the fruits have no definite dehiscence mechanism; in 

 others they open by deliquescence or by a separation of plates. Some open by a 

 single pore, and appear transitional to those of order Sclerocarpa; some open by a 

 cleft, or by lobes separated by radiating clefts, and appear transitional to those of 

 order Phacidialea. 



Order 4. Phacidialea [Phacidiales] Bessey in Univ. Nebraska Studies 7: 298 

 (1907). 

 Phacidiacei Fries Syst. Myc. 1: li (1832). 



Order Hysteriaceae and suborders (of order Discomycetes) Phacidiaceae, 



Stictideae, and Tryblidieae Rehm in Rabenhorst Kryptog.-Fl. Deutsch- 



land 1, Abt. 3: 1, 60, 112, 191 (1896); the ordinal name preoccupied by 



family Hysteriaceae Saccardo. 



Suborders Phacidiineae and Hysteriineae Engier in Engler and Prantl Nat. 



Pflanzenfam. I Teil, Abt. 1 : v ( 1897) . 

 Orders Graphidiales and Hysteriales Bessey op. cit. 298, 303. 

 Order Hemisphaeriales Theissen in Ann. Myc. 11: 468 (1913). 

 Order Microthyriales Clements and Shear Gen. Fung. ed. 2: 94 (1931), 

 Ascomycetes producing fruits which are not typical cleistothecia, apothecia, or 

 perithecia. 



This group is here used as a catch-all for three or more distinct groups, which 

 appear to form cross-connections among orders Perisporiacea, Cupulata, and Sclero- 

 carpa. This appearance suggests the probability that the present group, and the 

 usually accepted orders assembled under it, are not natural, but represent parallel 

 developments from several sources. The present groups include moderately numerous 

 ordinary parasites and saprophytes, together with great numbers of lichen-formers. 

 Only the latter are common and familiar in temperate countries. There has been little 

 study of the morphology. 



The families which appear tenable are distinguished as follows: 



a. Fruits minute and flattened, usually releasing the spores through one or more 

 pores or clefts (Order Hemisphaeriales Theissen, Microthyriales Clements 

 and Shear). 



