304 THE LOWER FUNGI— PHYCOMYCETES 



the central cavity of the fruit body led van Tieghem to regard the 

 latter as a multispored ascus. The papers of Barker (1903), 

 Ikeno (1903), and OHvc (1905) have clarified the situation. 

 The position of the Aspergillaceae in the classification is dis- 

 cussed below. The genera Helicosporanghim and Papulaspora 

 have been studied in recent years by Hotson (1912). He merges 

 them under the latter name, and regards the group as a form 

 genus characterized by peculiar vegetative structures called 

 bulbils which are evidently merely sclerotia of loose structure. 

 The genus must be included in the group of sterile fungi with 

 such genera as Ozonium, Sclerotium, and Rhizoctonia. Its 

 species have been shown to have fruiting stages representative of 

 various groups of the fungi. Complete misinterpretation of the 

 nature of the bulbil led to the inclusion of these forms in the 

 Hemiascomycetes. 



The family Protomycetaceae, as treated by Schroter, includes 

 two genera Protomijces Unger (1833) and Endogone Link (1809). 

 These are not in fact closely related. Endogone has been dis- 

 cussed in a preceding chapter as a member of the Mucorales. 

 As now understood the Protomycetaceae include three genera, 

 Protomyces, Protomycopsis, and Taphridium. These constitute 

 a coherent group of definitely related forms. The species are all 

 parasitic in higher plants. The mycelium consists of delicate, 

 intercellular, septate, branching hyphae, which bear large, 

 globose to ellipsoidal, thick-walled, unicellular chlamydospores 

 as terminal or intercalary enlargements. The chlamydospore 

 after a period of rest germinates by the rupture of the thick 

 exospore and the extrusion of the thin endospore as a globose 

 or cylindrical sac. The contents of the chlamydospore, before 

 or after passing into the sac, are broken up into a large 

 number of small unicellular spores. These are disseminated by 

 the violent apical rupture of the sac, and after their escape may 

 undergo copulation in pairs. In germination they produce the 

 endophytic mycelium directly, or in nutrient solutions bud like 

 yeasts. The chlamydospore is multinucleate in young stages 

 and is probably so from the first, the nuclei being scattered 

 without order throughout the cytoplasm. In Protomyces and 

 Protomycopsis they pass over thus with the cytoplasm into the sac- 

 like extruded endospore (Fig. 109). Vacuoles then appear, and 

 when the sac is fully formed the cytoplasm and nuclei constitute 

 a thin peripheral layer surrounding a single large central vacuole. 



