210 THE ASCOMYCETES 



Conidial stages are uncommon, but Peziza repaiida, P. vesicu- 

 losa, and Patella abiindans are reported to posses^ conidia. In 

 P. abiindans the conidia are of the Botrvtis type. 



The Pezizales generally are not restricted to a particular sub- 

 strate, most of them occurring on moist soil high in organic con- 

 tent or on decaying wood. Some species, however, are quite 

 restricted in substrate and range. Pyronevm cojifluens is com- 

 monly found on burnt ground at the sites of campfires and has 

 been observed to produce a copious pinkish cover upon the 

 surface of pots of soil sterilized by steam. Corner (1930) records 

 having seen millions of apothecia of AntJoracobia nmiirilabra 

 on several acres of burnt ground in England. During rainy 

 weather Pithy a ciipressi may densely occupy the recently killed 

 branches of Juniperus and related conifers. Urnula geaster is 

 limited to the vicinity of decaying stumps of Ulvnis crassifolia. 

 Some species are coprophilous, and species of Ascobolus, Asco- 

 desmis, Ascophanus, and Ryparobius are limited to the dung of 

 certain animals; Ascodesmis porcina, for example, occurs only 

 on pig dung. 



Apothecial development. Sexuality and the development of 

 apothecia among Pezizales have been extensively studied by 

 Harper (1900), Dangeard (1907), Claussen (1912), Dodge 

 (1912), Dowding (1931), Schweitzer (1931), and Gwynne- 

 Vaughan and Williamson (1932). Pyronema confluens and sev- 

 eral species of Ascobolus have been employed in these studies. 

 Pyroneina confluens has large vesiculate, multinucleate ascogonia. 

 Clavate, multinucleate antheridia arise near the ascogonia, each 

 surmounted by a curved hypha, the trichogyne. The multinu- 

 cleate protoplast from the antheridium empties, by way of the 

 trichogyne, into the ascogonium. Soon ascogenous hyphae arise 

 from the surface of the ascogonium, from the penultimate cells 

 of whose recurved tips the asci are developed. 



Two opposed views are held concerning nuclear activities. 

 Harper (1900) maintained that the nuclei fuse in pairs within the 

 ascogonium and again in the base of the developing ascus, thus 

 making the primary nucleus of the ascus tetraploid. This view 

 is supported by Gwynne-Vaughan and Williamson (1932), who 

 found that the chromosome number in spore nuclei and in the 

 nuclei of sterile tissue is 6, whereas that in nuclei of the ascog- 

 enous hyphae is 12. Moreover, they found that the number of 



