314 



CLASS ASCOMYCETEAE 



Fig. 100. Erysiphales. (A) Family Erysiphaceae. Microsphaera quercina (Schw.) 

 Burr. Vertical section through an almost mature perithecium. At right and left are 

 the bases of two appendages. (B) Family Meliolaceae. Parodiopsis stevensii Arn. 

 Vertical section through almost mature perithecium. (Courtesy, Arnaud: Ann. sci. 

 nat. Botan., 7:643-723.) 



From the outer cells of the cortex, mainly near the equatorial zone, 

 arise the characteristic appendages. These are simple and hypha-like in 

 Erysiphe, Leveillula, Sphaerotheca, Chilemyces, and Leucoconis, hooked or 

 spirally-coiled at the tip in Uncinula and Uncinulopsis, straight and once 

 or more dichotomously forked at the apex in Microsphaera, Podosphaera, 

 and Schistodes, or stiff and needle-like, with a bulb-like base, in Phyllac- 

 tinia. In some species the appendages are colorless, but often they are 

 colored basally. They do not seem to have the same function in all cases. 

 They may hold the perithecia fast to the mycelium or may push it up 

 above the surface of the mycelium, or may curve downward and pry the 

 perithecium loose, as in some species of Uncinula and in Phyllactinia. 

 The hooked or forked appendages would seem fitted for distribution by 

 insects, but that has not yet been demonstrated to be the normal means 

 of distribution. The upper half of the perithecium of Phyllactinia and of 

 Typhulochaeta bears short, penicillately branched mucilaginous cells. 

 These serve to fasten the perithecium, after its separation from the 

 mycelium, with its top side down, to objects with which it comes into 

 contact. Appendages are lacking in AstomeUa. (Fig. 101.) 



When the ascospores are mature, which may not be until the following 

 spring, the asci and the inner cells of the perithecium absorb water and 

 swell until the perithecium is ruptured, at which time the asci also begin 

 to burst, discharging the enclosed ascospores with considerable force, or 

 when the perithecium bursts it may throw out the asci still containing 

 their spores. 



Homma (1933) sowed a single conidium of Sphaerotheca fuliginea 

 (Schlecht.) Pollacci upon its host plant and on the resultant mycelium 

 were produced conidia and sexual organs. He therefore considered this 



