71 



MORPHOLOGY 



"swollen hypha " represents the female sex organ, which by fertilization 

 or not becomes the ascogonium. 



Applying these facts to Peziza and to the other Pezizales, it is probable 

 that in them an ascogonium related to a sexual act is present either 

 actually or historically; and that the nuclear fusion, which represents 

 the essential feature of fertilization, is likely to have persisted in the 

 life history even though apparent sex organs may have disappeared. 



(e) Tuberales 



These are the truffles, whose mycelium is entirely subterranean in humous soil. 

 A remarkable subterranean, tuber-like, fleshy ascocarp is produced, which is the 

 edible truffle. The ascocarp completely incloses the asci, and this closed type is 

 often designated a cleistothecium, to distinguish it from the open ascocarps (apothe- 

 cia). The cleistothecium of Tuberales consists of a fleshy cortex and a central 

 ascus-forming region. In maturing, the interior sterile tissue and the asci disappear, 

 leaving the ascospores free within the cortex. Very little is known of the life 

 history of the Tuberales. It has been suggested that the mycelium may be that 

 of some root fungus (mycorhiza), for in France and Italy, the chief market sources 

 of the truffles of commerce, they are found constantly under oak trees. 



(f) Plectascales 



This group comprises saprophytes with an extensive mycelium, closed 

 ascocarps (cleistothecia) of peculiar structure, and abundant produc- 

 tion of conidia. The best-known repre- 

 sentatives are the blue and green molds: 

 Aspergillus (Eurotium), the herbarium 

 mold, also on bread, preserves, etc.; and 

 Penicillin m, the common blue mold on 

 bread, etc. From the mycelia the 

 sporophores (conidiophores) arise in 

 profusion, and their terminal branches 

 by abstriction produce rows of conidia 

 (fig- 179)- 



The sex organs are represented by 



two short, spirally intertwined filaments. 



Fig. 179.— Penicillium: branches Their fusion has not been recorded, but 



of a sporophore producing rows of f rom one f) f tne m ascogenous hyphae 



conidia. , , ,, 



arise and bear numerous small asci con- 

 taining eight ascospores. At the same time, the usual investment of 

 sterile filaments is developed and forms a compact, parenchyma-like 



