160 



Mycologia 



is fully developed, the first evidence of conidial formation con- 

 sists in the dissolution of its apical wall. This is followed by the 

 protrusion of the protoplast (Fig-. 14) which is surrounded by a 

 thin membrane. The protoplast enlarges greatly and becomes 

 more or less pyriform with the narrow portion fitting as a plug 

 into the mouth of the conidiophore (Fig. 15-17). Meanwhile, 

 a septum delimiting the first pear-shaped conidium is being 

 formed a short distance back of the mouth. The continued 

 growth of the protoplast behind this conidium forces it beyond 

 the mouth of the conidiophore. The apical portion of the en- 

 larging protoplast then becomes delimited, forming the second 

 conidium in a manner entirely similar to the first. 



Olive conidia vary greatly in size and shape (Figs. 13, 15-17). 

 In case formation progresses rapidly so that each conidium is 

 pushed beyond the mouth of the conidiophore before its wall 

 thickens, pressure within the conidium causes it to assume an 

 elliptical shape. On the contrary, when conidial formation is less 

 rapid, and the wall of a conidium becomes rigid before it is 

 entirely without the conidiophore, its original pyriform shape is 

 retained. 



When first formed, these conidia are hyaline, but within 48 

 hours become olive-brown. They have a granular protoplasm 

 having a varying number of oil droplets, the reserve food (Figs. 

 15, 17). As the conidia become older, the brown wall becomes 

 thick and resistant (Figs. 18, 19). When these are placed in 50 

 per cent, sulphuric acid solution, the outer heavy wall bursts 

 and a very thin, hyaline-walled vesicle slips out. Within a few 

 moments this ruptures, liberating the protoplasmic contents. 

 Most olive conidia range in size from 12 to 16 by 8 to 12 a 

 few being larger or smaller. In old cultures the smaller conidia 

 predominate. 



Discussion 



Upon comparing the account of conidial formation given above 

 with that for Thielavia basicola by Brierley (4), certain essen- 

 tial points of difference can be noted : 



1. If the first conidium of Sphaeronema fimbriatum were pro- 

 duced, as in Thielavia, by direct septation of the conidiophore and 



