iqiq] KEMPTON—PYCNIDIUM 237 



Phoma pirina (Fries) Cooke; isolated at Urbana, Illinois, May 10, 

 1916, from dead twigs of Pyrus communis L. from Savoy, Illinois. 



This fungus produces abundant small pycnidia 60-120 ju in 

 diameter, at first closed but later with an ostiole 20-30 jx wide. 

 The spores vary in size from 5X3toioX4M. A few cells of the 

 hypha swell, divide both crosswise and diagonally, swell, and divide 

 again (figs. 6, 7). This small mass continues to enlarge by cell 

 division, and a few hyphal branches bud out from it (fig. 8). By 

 continued development an irregular mass (fig. 9) is formed, which is 

 the primordium of the pycnidium. In a few cases closely lying 

 hyphae may take part in the formation (figs. 10-13), but the 

 typical method of development is the simple meristogenous one 

 from a few cells of a single hypha. 



Phoma destructiva Plowr.; isolated at Urbana from fruits of 

 tomato {Lycopersicon esciilentum Mill.) in September 19 15. In 

 all respects the disease and the fungus agreed with the one described 

 by Miss J.\mieson (22) . 



The pycnidial primordium usually arises meristogenously. In 

 most cases a single hypha gives rise to the primordium (figs. 14-17) ; 

 in other cases 2 or more hyphae share in its formation (figs. 18, 19, 

 22). In either case adjacent cells swell and divide crosswise and 

 diagonally until a rounded or elongated mass is formed, slightly 

 darker in color thAn the mycehum. The former (fig. 15) is the 

 simple type of meristogenous development. 



Phoma, species indet.; isolated from stems of clover {Trijolium 

 pratense L.) at Urbana, Illinois, in July 1916. 



Development takes place in a simple meristogenous manner. 

 One hypha only is involved in the formation of the primordium 

 (figs. 23-27). Short hyphal threads sometimes branch from the 

 mass. The cells are usually large and swell into a rounded shape. 

 The mass develops more rapidly at one end than at the other, so 

 that the young pycnidium is slightly conical. 



Phoma, species indet.; isolated from a berry of the Concord 

 variety of grape {Vitis labruscaL.), from a vineyard near ColHns- 

 ville, Illinois, September 191 7. 



A portion of the culture seen under the high power of the micro- 

 scope showed a very characteristic arrangement of hyphae and of 



