878 LIFE-HISTORY OF PHOMA CITRICARPA, 



The following stages may be distinguished in the production 

 of a pycnidium :— 



1. Production of lobulated hypliae, which become interwoven. 



2. Formation of a pseudo-parenchyma. 



3. Dissolution of cell-walls of the pseudo-parenchyma at certain 

 foci, followed by formation of hyphse. 



4. Establishment of loculi at these foci, into which spores are 

 abstricted from the hyph^e. 



5. Gradual replacement of the pseudo-parenchyma by spore- 

 bearing hyphie. 



6. Shrinkage of the spore-bearing hyphae. 



7. Pycnidium completely full of spores borne upon attenuated 

 stalks. 



The transition from pseudo-parenchyma to spore-bearing hyphie 

 is shown in PL Ixxxix., figs. 20, 21. A portion of the pseudo- 

 parenchyma frequently lines the pycnidium until a late stage. 



In the natural state, when growing upon the orange, the 

 pycnidiaaregenerally unilocular (PL xc, fig. 22). But, in cultures 

 upon orange-agar, they are frequently bi- or trilocular, in which 

 case, the loculi are surrounded by a common wall (PL xc, fig.23). 



In bilocular pycnidia, portions of the inner parenchymatous 

 tissue have become firm, and the groups of thin-walled hyphse 

 have become separated. 



Pycnidial formation has been briefly described in the case of 

 Diplodia zece by Van der Bijl(7), and in the case of Phoma 

 lavamluhe by W. B. Brierley(8). 



The origin of the pycnidium by the interlacing of lobulated 

 hyphse with the formation of a pseudo-parenchyma is very similar 

 in Phoma cilricarpa and I'h. lavaaduUn. The later stages in the 

 development of the pycnidium of Ph. citricarpa resemble the 

 description given of that of Diplodia zece. The marked visiijility 

 of the protoplasm lining the cells of the pseudo-parenchyma, and 

 the disappearance of the cell- walls previous to the formation of 

 hyphae, described in the case of Fh. citricarpa, is not mentioned 

 by the authors quoted. 



The formation of hyphse from naked protoplasm is not un- 

 known, as it occurs in the Myxomycetes, when the capillitium, 



