igig] KEMPTON—PYCNIDIUM 239 



have no part in its formation. The body thus developed is the 

 primordium from which the pycnidium arises. It continues to 

 enlarge, becomes pear-shaped, forms an ostiole, and develops 

 spores. This mode of development is meristogenous, with a slight 

 modification in that short hyphal branches either fuse with or 

 form an envelope about the primordium. 



Less frequently a second method appears, in which short 

 branches from main mycelial strands direct themselves toward a 

 point. There these branches interweave, swell, and divide to 

 form a network (fig. 48). This network is at other times formed 

 by the looping back or snarling of hyphal branches. The tangle 

 enlarges, becomes more tightly woven, then the cells divide, swell, 

 and anastomose to form a pseudoparenchymatous mass (fig. 49). 

 This method is symphogenous. This species gives rise to both 

 meristogenous and symphogenous developments. 



The pycnidia of the species studied in the genera Phoma and 

 MacropJwma indicate that both meristogenous and symphogenous 

 methods of development may be found. These species present in 

 the main the simple meristogenous mode in which a few cells of a 

 single hypha take part (figs, i, 6, 15, 23, 29, 38, 44); also a slight 

 variation of the simple development in which hyphal branches 

 both from the dividing cells and from other cells of the mother 

 hypha form a network about the original cells taking part in the 

 development . (figs. 36, 39, 47). The compound meristogenous 

 development is that in which 2 or more main hyphae, lying parallel 

 or crossing, begin to divide into short cells at a point of contact, 

 swelling and dividing to form a primordium (figs. 18, 22, 37). 

 A few adjacent cells of each hypha and some surrounding branches 

 take part in this type of development. 



Sphaeronaema Fries 



Sphaeronaema fimbriatum (E. and H.) Sacc; procured from 

 Dr. Byron D. Halsted, October 1916. 



Halsted and Fairchild (18) report and figure the develop- 

 ment of the pycnidium of Ceratocystis fimbriaia as follows : 



In its initial stages the pycnidium arises as the swollen and curled or 

 twisted tip of a vegetative hypha, or as a twist or knot in a sporophore between 



