286 CLASS ASCOMYCETEAE 



or in a stroma. A further group includes forms in which the perithecia 

 buried in the stroma do not have well-developed walls of their own but 

 represent perithecial cavities in the stroma. Only this last type does not 

 have its counterpart in the Sphaeriales. The ascospores, as in the latter 

 order, vary from ellipsoidal and one-celled to two-celled, phragmosporous, 

 muriform, or even thread-like. Some are brown but the majority are hya- 

 line or bright-colored. Conidial fructifications are rather widespread in 

 this order. The conidiophores may be separate and external or they may 

 be packed closely together side by side or may be enclosed in a pycnidium 

 or united into a stalked head {Stilhella type). Many of the approximately 

 1000 species are saprophytic; others are parasitic in the leaves, stems, and 

 roots or other portions of higher plants; still others are parasitic on fungi 

 or upon insects. 



The course of sexual reproduction has been worked out completely in 

 a few forms, but, as mentioned for the Sphaeriales, only enough is known 

 to make certain that vastly more must be found out before the knowledge 

 may be used to modify the current system of classification. The latter, 

 as in Sphaeriales, is largely based upon the characters of the mature 

 perithecium. 



In a number of Hypocreales a coiled ascogonium and antherid are 

 known. In Polystigma ruhrum (Fr.) DC, parasitic in the leaves of the 

 plum (Prunus domestica L.), Blackman and Welsford (.1912) and Nienburg 

 (1914) have shown that the ascogonium is a stout hypha with several 

 coils of mostly plurinucleate cells and tapering into a slender, sometimes 

 branched, trichogyne which may extend through a stoma but apparently 

 more frequently does not do so. Organs exist which have been called 

 spermogonia. Whether they really are properly so called remains in 

 doubt. They usually appear some time after the ascogonia, and their 

 spores are long and slender and curved like some of the conidia of the 

 Diaporthaceae. No connection between one of these spores and a tricho- 

 gyne has been observed. Eventually, according to Nienburg, the wall 

 breaks down between a multinucleate ascogonial cell and the large uni- 

 nucleate oogone cell next to it and one nucleus passes into the oogone. 

 Later ascogenous hyphae are sent out from the latter and eventually give 

 rise to asci. Blackman and Welsford disagree with the foregoing and claim 

 that the ascogonium degenerates and that the ascogenous hyphae arise 

 from near-by vegetative hyphae. In Claviceps purpurea (Fr.) Tul., ergot, 

 the germinating sclerotia give rise to stalked heads in which arise the 

 perithecial primordia. This consists for each perithecium, according to 

 Killian (1919), of a multinucleate rounded oogone from whose base 

 branch out one or two antherids which also have many nuclei. One of 

 these antherids comes into contact with the oogone at its tip and an 

 opening is formed through which the male nuclei enter. This gives rise, 



