2i8 RESEARCHES ON FUNGI 



filled with dense protoplasm, but sooner or later its basal end becomes 

 vacuolated (Fig. 107, C and E). As a promycelium increases in 

 length, the protoplasm creeps along it acropetally, always filling the 

 apical end. As the protoplasm migrates along the tube, septa are 

 formed at intervals in such a way as to cut off those parts of the 

 promycelium which have become devoid of protoplasm (Fig. 107, 

 C, E, F). In very short promycelia one can usually observe at least 

 one septum, while in long ones there may be a dozen or more. Not 

 infrequently one may observe branched promycelia (Fig. 107, D), 

 but these appear to be abnormalities brought into existence by 

 unsuitable cultural conditions. 



From the fourth to the eighth day, when germination is pro- 

 ceeding normally, the end of the promycelium grows away from the 

 substratum as if it were negatively hydrotropic, enlarges at its apex, 

 and produces peripherally a number of very short protuberances 

 some of which may fork once (Fig. 107, E, just below p). From the 

 ends of these protuberances there then grow upwards from four to 

 sixteen primary conidia (Fig. 107, E and F). These conidia take 

 four hours or somewhat longer for their full development from tiny 

 rudiments. When fully grown, a conidium is 70-80 ju long, about 

 4 jj. wide in the middle, about 2-3 (i wide at its base, and pointed at 

 its apex. Several observers have incorrectly represented the primary 

 conidium as tapering to a fine point at the base as well as at the apex. 



The work of Rawitscher x has shown that two nuclei, presumably 

 of opposite sex, fuse together in the young chlamydospore ; that the 

 reduction divisions take place in the chlamydospore ; that, as a 

 rule, three nuclear divisions succeed one another, so that eight 

 daughter-nuclei come to be present in the chlamydospore ; that 

 some of these nuclei may divide again, so that often a total of 8-16 

 nuclei may be produced ; that these nuclei wander out of the 

 chlamydospore into the promycelium ; that the number of primary 

 conidia formed at the apex of the promycelium is equal to the 

 number of nuclei which the promycelium contains ; and that a 

 single nucleus passes into each primary conidium. 



During the development of the primary conidia, as may be seen 



1 F. Rawitscher, " Beitrage zur Kenntnis der Ustilagineen," Zeitschr. f. Bot., 

 Bd. II, 1922, pp. 273-296. 



