210 



COMPARATIVE MORPHOLOGY OF FUNGI 



direction of the Sphaeriales, it may become many layered. In many 

 species, as in Erysiphe and Leveillula of the Erysiphaceae, it is symmetri- 

 cal throughout the fructification; in others, as in Microsphaera and 

 Uncinula, it is dorsiventral and is drawn out to a small wart or papilla 

 at the tip; in other species, as in Meliola corallina (Fig. 132, 2), as a 

 definite step in the direction of the Sphaeriales, a true opening, an ostiole, 

 is formed at the top of the perithecium (Bucholtz, 1897). At times the 

 perithecia, as in the Erysiphaceae, are provided with appendages, or peri- 

 thecial spines, which, however, are only simple, unbranched and generally 



Fig. 134. — Parodiopsis Stevensii. Development of stomatopodia. 1. Seen from 

 above. 2. In section (X670). Parodiopsis megalospora. 3. Section showing intra- 

 matrical mycelium (X 530). {After Arnaud 1921, 1923.) 



not numerous. Where complicated structures are described, there seems 

 to have been a confusion with mycelial spines which rise below the 

 perithecium. 



The asci (another transition from the Plectascales to the Sphaeriales 

 type) are generally spherical, rarely clavate. They usually contain only 

 2 to 4 brown, multiseptate spores. 



From Balladyna and Meliola, the development proceeds in two 

 directions, one blindly from Balladyna to the Englerulaceae, the 

 other progressively from Meliola to the Sphaeriales. As we shall briefly 

 discuss the Englerulaceae as a third family of the Perisporiales, the step 

 to the Sphaeriales will be described here ; it is completed by Parodiopsis. 

 In this genus, the transitional character of the Perisporiales appears with 



