PERISPORIACE^E. 151 



occurrence, especially in vegetable putrefactions. It grows 

 readily in gelatin. It consists, to the naked eye, like the other 

 fungi described, of a mass of felted filaments which microscop- 

 ically are seen to form a septate branching mycelium. Though 

 it is a matter of doubt whether sexual reproduction takes place, 

 two forms of reproduction occur, the variety depending largely 

 on the nutrition of the plant. The less common form is effected 

 by means of the formation of structures known as perithecia, 

 and it may perhaps be that the perithecia owe their formation 

 to a sexual act. From a mycelial branch there arises a filament 

 (or hypha) which becomes specially coiled and transversely sep- 

 tate at its end. From the base of the lowest coil of the spiral 

 two or three hyphae grow up towards its apex. One of these, 

 being the first to reach the apex, was regarded by De Bary as 

 a male organ. The others, by branching copiously, produce a 

 mass of closely woven hyphae, which form a closed wall to this 

 structure, which is the perithecium referred to. Within it nu- 

 merous asci arise as the ultimate ramifications of branches given 

 off by the central coiled hypha. Inside each ascus eight asco- 

 spores are produced. Ultimately all the structures lying within 

 the perithecium, save the spores, undergo disintegration, so that 

 the mature perithecium consists of a small hollow sphere within 

 which lie the loose spores. These latter are ultimately freed by 

 the decay of the wall of the perithecium and develop into new 

 individuals. The commonest method of reproduction is by the 

 formation of spores (gonidia or conidia), which are clearly of 

 non-sexual origin. These are formed externally in the hyphae 

 and not inside sporangia. A filament grows out, and at its ter- 

 mination a club-shaped swelling is formed on which a series of 

 flask-shaped cells, called sterigmata (vide Fig. 61, C6), are 

 perched. At the free end of each of these, an oval body, the 

 spore or gonidium is formed, and this becoming free, can give 

 rise to a new individual. 



(2) Penicillium Glaucum. This is perhaps the most com- 

 mon of all the fungi met with in bacteriological work. It is 

 the common green cheese mould, and its spores are practically 

 omnipresent. The mycelium is like that of the aspergillus. 

 Perithecium formation takes place, but the commonest mode of 

 reproduction is by gonidia (vide Fig. 61, D). A filament (called 

 a gonidiophore) grows out, and at its end breaks up into a num- 



