74 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 
Penicillium, 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 o f t h em aSCOgenoUS hyphae 
conidia. 
arise and bear numerous small asci con- 
taining ejght ascospores. At the same time, the usual investment of 
sterile filaments is developed and forms a compact, parenchyma-like 
