ORDER ASPERGILLALES (PLECTASCALES) 325 



portion of the perithecium we would have the structure as it is found in 

 the Aspergillaceae. If the central and cortical tissues of the perithecium of 

 the latter instead of forming a continuous structure should remain more 

 or less loose and cottony we would have the Gymnoascaceae. If the peri- 

 thecium should become much enlarged (up to several centimeters) with a 

 firm cortex several layers of cells thick and a more or less permanent mass 

 of loose central tissue traversed by more or less well-developed sterile 

 "veins," in which the asci are scattered, the structure would be that of 

 the Elaphomycetaceae. In the Onygenaceae the ascocarp is differentiated 

 into a basal sterile portion and a somewhat larger head in which the asci 

 are scattered in a central mass of tissue which eventually breaks up into 

 a sort of capillitium. The Trichocomaceae are forms whose development 

 is not well understood and whose relationship to other families of the order 

 is more or less a matter of doubt. The Terfeziaceae, placed by Fischer 

 (1896) in this order were more recently (1938) placed by him in the 

 Tuberales. Myriangium and probably several other genera rather similar 

 in structure, forming the Family Myriangiaceae, possibly also belong in 

 this neighborhood but are better placed in a distinct order. 



Family Aspergillaceae. The chief genera of this family are the 

 ubiquitous molds, PenicilUum and Aspergillus, of which the commonest 

 species are the blue and green molds found on all sorts of organic matter. 

 Most of their species are saprophytes but a few are animal parasites, caus- 

 ing cases of mycosis. The small orange or yellow perithecia of a species of 

 Aspergillus (perhaps more properly called Eurotium) are very frequently 

 found on jams and various conserves, as well as on imperfectly dried 

 herbarium specimens where it is called ''herbarium mold." Usually when 

 examined these are found to consist of nothing but a thin peridium sur- 

 rounding a cavity in which are found a large number of ascospores shaped 

 much like a pulley wheel. Rarely a few asci will be found but usually their 

 thin walls have completely dissolved away. In PenicilUum perithecia are 

 much more rarely formed and are more often sclerotium-like. The two 

 genera are best distinguished by their conidiophores. In Aspergillus the 

 conidiophore is swollen at its apex into a head from which radiate numer- 

 ous short sterigmata bearing at the apex of each a chain of spherical or 

 nearly spherical, smooth or roughened conidia, or sometimes producing 

 secondary sterigmata which bear in their turn the chains of conidia. The 

 species with the secondary sterigmata were formerly set apart in the 

 genus Sterigmatocystis but the modern usage is to include these in Asper- 

 gillus. In PenicilUum the conidiophore branches several times without 

 enlarging, the terminal portions lying more or less parallel, or at least not 

 widely divergent, and bearing one to three or four sterigmata with chains 

 of conidia. Thorn (1914) described in detail the method of formation of 

 the conidia of this genus. From the apex of the sterigma is produced a 



