VOLUME LXVIII NUMBER 4 



THE 



Botanical Gazette 



OCTOBER igig 

 ORIGIN AND DEVELOPMENT OF THE PYCNIDIUM 



F. E. Kempton 



(with plates xvii-xxii) 

 Introduction 



The Ascomycetes have been the subject of repeated investiga- 

 tions, especially in regard to the morphology of the perithecium 

 and the cytology and sexuaKty of the ascigerous stage. The 

 conidial stages, placed in the Fungi Imperfecti in the absence of 

 knowledge of their ascigerous stages, of necessity are classified 

 on a basis of the morphology of the conidia-bearing structures. 

 For this reason, and because the pycnidia are said sometimes to 

 develop directly into perithecia, extension of our knowledge of the 

 morphology of such conidiiferous structures as the pycnidium and 

 the acervulus is highly desirable. 



The references in literature to the development of the pycnidium 

 are, for the most part, merely incidental, and studies directly 

 devoted to the subject are few. As early as 1876 Bauke (5) 

 described what he considered as 3 methods of pycnidial devel- 

 opment, without giving names to them. In 1884, however, 

 DeBary (9) distinguished 2 main methods of development, 

 which he designated as " symphogenous " and "meristogenous": 

 " symphogenous " when the pycnidial primordium arises through 

 the interweaving of young hyphal branches to form a network that 

 is at first loosely woven, but later becomes compact and knotlike; 



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