156 



Mycologia 



the protoplast behind it, and a number of other conidia are 

 formed successively in the same manner. The mode of forma- 

 tion of the olive conidia differs from that of the hyaline conidia 

 only in that they are not produced so rapidly, and in such other 

 respects as are made necessary by differences in size and shape 

 of the conidia. 



Taubenhaus (2), in his studies of sweet potato black rots, 

 states that spore formation in Sphaeronema fimbriatum resembles 

 that in Thielavia in that " the spores are borne within the sheath 

 of a terminal cell, and these are pushed out from within." 



Concerning the manner of spore formation in Thielavia basi- 

 cola, Zopf (3) states that the conidia of Thielavia basicola are 

 formed in acropetal succession on short, several-celled conidio- 

 phores. The wall of each conidium becomes differentiated into 

 two lamellae, the inner of which becomes the lateral wall of the 

 conidium and the outer, the sheath out of which the conidia pass 

 successively. 



Gilbert (5) differing from Zopf's view, applies the term " endo- 

 conidia " to the spores of Thielavia basicola which " originate 

 within the terminal cell and are not formed by its direct 

 septation." 



Brierley's (4) conclusions from a study of conidial formation 

 in Thielavia basicola are at variance with both of these accounts. 

 He affirms that the conidia are not formed endosporously within 

 an endoconidial cell, but are acrogenously ab jointed from the 

 conidiophore. The first conidium is then liberated by a tan- 

 gential splitting of its walls, which thus become differentiated into 

 an outer closed sheath and an internal spore membrane. This 

 outer sheath then ruptures, freeing the first conidium. Conidia 

 subsequently produced are formed in the rear of the first in a 

 manner in all respects like that of the first. Brierley further 

 states that the process of conidial formation as he has described 

 it for Thielavia, is probably that of all other " endoconidia " in 

 fungi. 



Methods 



In order to facilitate the observations recorded in this study, 

 Sphaeronema fimbriatum was grown upon various substrata. 



