240 BOTANICAL GAZETTE [October 



the conidium and its point of union with the main hypha. Although observed 

 to be present in numerous cases, no anastomosing of different hyphae branches 

 seems necessary. Almost simultaneously with the first curving of the hypha 

 tip side branches arise, which, by their growth and formation of septa, form 

 the coarsely cellular membranous wall of the pycnidium. 



Single mountings from plate cultures gave all stages of develop- 

 ment verifying this description. The usual development was the 

 twisting, budding, branching, and enlarging by cell division of single 

 twisted hyphal branches (figs. 50-52). This is a variation of the 

 meristogenous development. 



Sphaeropsis Leveille 



Sphaeropsis malorum Pk.; isolated from apple fruits {Pyrus 

 mains L.) from Centerville, Indiana, in October 1916. 



Hesler (19) gives the development of the pycnidium of 

 Physalospora cydoniae Arnaud in agar cultures as follows : 



The dense pseudoparenchyma of the maturer fruit bodies suggests meri- 

 stematic divisions, but apparently the structure, for the most part, arises 

 symphogenetically. In agar cultures a group of threads may be observed to 

 be directed toward a common point where the pycnidium is to be formed. 

 Here the hyphae are composed of cells 6-7 fi broad, their length varying from 

 20 to 70 fi., always longer than broad. In the region where the pycnidium is 

 to be developed, the cells become noticeably shorter by the laying down of 

 new walls; the cells also increase in diameter by growth, and the hyphae 

 increase their numbers by branching. The interspaces found in the earlier 

 stages are fiUed by the growing in of these branches and by a budding-like 

 action of the hyphal cells bordering the space. 



Among my own notes upon Sphaeropsis malorum Pk., made 

 before the appearance of this description, is an account of the 

 development of the primordium which it seems worth while to 

 give here. 



The pycnidial primordium of this species is formed usually 

 according to the method designated by DeBary as symphogenous. 

 A number of hyphal branches interweave near their ends (fig. 53) ; 

 these in turn branch and the branches also interweave (figs. 54, 

 55). The central portion becomes a tightly woven mass. The 

 whole continues to enlarge until a spherical mass is formed, which 

 develops into a pycnidium. Most of these primordia form deeply 



