CONIDIAL FORMATION IN SPHAERONEMA 

 FIMBRIATUM 1 



S. G. Lehman 2 

 (With Plate 7, Containing 19 Figures) 



During the past two years, a study has been made of the 

 morphology and development of Sphaeronema fimbriatum (Ellis 

 & Hark.) Sacc, a fungus causing a black-rot disease of the 

 sweet potato (Ipomoea batatas). This organism is known to 

 give rise to propagative bodies of several types, one of which is 

 designated as hyaline conidia, another as olive conidia. The ac- 

 counts by previous investigators are not entirely concordant, and 

 certain of them appear to inadequately describe and interpret the 

 formation of these structures. The purpose of this paper is, 

 therefore, to set forth in detail the manner of formation of these 

 two types of conidia and to compare these structures with the 

 so-called endoconidia of Thielavia basic ola Zopf . 



While it is entirely beyond the scope of this article to review 

 the literature on endoconidial formation in fungi, a proper under- 

 standing of the present problem necessitates a summary of the 

 most important investigations on Sphaeronema and Thielavia. 

 According to the account of Halsted and Fairchild (i), who first 

 made a detailed study of Sphaeronema fimbriatum, the proto- 

 plast of the conidiophore which produces hyaline conidia rup- 

 tures or absorbs the apical wall of the conidiophore. A septum 

 is then formed below the mouth of the conidiophore, thus cutting 

 off the end of the protoplast to form a conidium. This conidium 

 is pushed beyond the mouth of the conidiophore by growth of 



1 This paper is taken from a thesis presented to the North Carolina State 

 College of Agriculture and Engineering in partial fulfilment of the require- 

 ments for the degree of Master of Arts. 



2 The writer is greatly indebted to Dr. F. A. Wolf for many helpful sug- 

 gestions during the progress of the work and for aid in preparing the manu- 

 script. 



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