104 MEDICAL MYCOLOGY 



split, the partial sporangia divide into oidial members, each of which contains 

 a spore ; thus the spores are completely surrounded by a sporangial wall, in- 

 separable from their own wall. 



The functionless sporangium remains in open connection with the sporifer- 

 ous hypha ; it remains capitate and does not collapse until after the maturing 

 of the partial sporangia. It may be regarded as a degenerate form only in 

 so far as the sterile inner part is no longer separated from the peripheral 

 spore protoplasm by the columellar wall. In Piptoceplialus, the sporangium 

 loses its capitate form, and shrinks to a verrucose basal cell, with an apical 

 partial sporangium which the degeneration of the basal cell frees from the 

 sporiferous hypha (Brefeld 1872, Tieghem 1875). The partial sporangia break 

 up into monosporous members whose sporangial wall is fused with the spore 

 membrane. The sporangiophores, therefore, have become conidiophores, rec- 

 ognizable as sporangiophores only through their phylogeny. 



In the Thamnidium-Chaetocladium series, the sporangiospores are nu- 

 merically much reduced, their functions being assumed by sporangia which 

 successively degenerate to conidia. In Tliamnidium elegans, the main axis 

 possesses an apical multispored sporangium which has a columella. Under 

 certain conditions, dichotomous branches terminating in sporangia are formed 

 from the main axis. These sporangia, however, are smaller than the terminal 

 ones, have no columella, become loosened as a whole from the sporangiophores, 

 and contain few, generally 4, spores. Spores are liberated not by deliquescense 

 but by disintegration of the sporangial wall. kSuch reduced sporangia are 

 called sporangioles. The spores in both types of sporangia behave similarly 

 as regards germination and further development. "When well nourished, the 

 sporangioles persist through several generations and finally become as large 

 and multispored as the sporangia. Conversely, with poor food supply a termi- 

 nal sporangium may turn into a sporangiole, often containing but one spore. 



This line of development is continued through Chaetostylum Fresenii 

 (Thamnidiuni chaetocladioides) . Here true sporangia are borne only with 

 adequate nourishment, while Avhere the food supply is limited, the terminal 

 sporangia abort. 



The terminal sporangia which have declined in these two species, disap- 

 pear in Chaetocladium, where the sporangioles also degenerate. They become 

 monosporous, the spore membranes fusing with sporangial walls. In Chaeto- 

 cladium Jonesii this double nature of the spore wall is evident, for on germina- 

 tion the sporangial wall separates from the spore. In C. Brefeldii, however, 

 this differentiation disappears, and the germ tubes protrude directly from the 

 wall. Again the sporangium has been transformed to a conidium. 



In another series, Mortierella and Haplosporangium show a similar degen- 

 eration. The sporangium of Mortierella is separated from the sporangiophore 

 by a septum (Fig. 8). Since its contents are not differentiated into fertile 

 and sterile zones, the spores arise directly by cleavage of the whole proto- 

 plasm. Their number is notably reduced, in some species to 2 or 4. Haplo- 



