DEVELOPMENT OF THE PERITHECIUM. 23 



or three times their diameter they suddenly break up into a number of 

 very fine, thread-like branches, which bud out from their upper ends 

 and grow on up to a height about equal to that of the unbranched basal 

 portion of the cell. This is the simplest type of these cells in the forms 

 of Phyllactinia I have studied. Much more abundant are other types 

 which, before breaking up into the ultimate thread-like branches, divide 

 first into two or three main branches, which may be very unequal or 

 approximately equal in size (fig. 51). As a rule this latter type of 

 cells lies farther away from the apex of the perithecium, and hence, 

 owing to its curved surface, must grow higher in order to bring the 

 ends of the filamentous branches to a level with those of the more cen- 

 trally placed brush cells. The penicillate cells begin their development 

 some time after the fusion of the nuclei in the ascus is complete, and 

 have completed their growth, as a rule, before the nucleus of the ascus 

 begins to divide preparatory to spore formation. The penicillate cell is 

 never divided, but remains throughout simply an enlarged and branched 

 peripheral cell of the perithecium. It contains two or three nuclei, as 

 a rule, before its special growth begins, and when fully developed may 

 contain as many as eight or ten nuclei. These are always situated in 

 the enlarged basal portion of the cell and never penetrate into the fila- 

 mentous branches. They form generally an irregular, scattered group 

 in the upper part of the basal portion of the cell (fig. 51) . 



As soon as, or even before, the penicillate cell reaches its full size 

 the walls of the filamentous branches begin to swell and become gelati- 

 nous. As a result they become fused together laterally to form the 

 slimy mass crowning the perithecium which has been described by many 

 authors. The wall and contents of the basal portion of the cells remain 

 unchanged for some time (fig. 51), but gradually it, too, is more or less 

 involved in the degenerative processes, and almost the entire walls and 

 contents of the penicillate cells are ultimately converted into a sticky, 

 gelatinous mass. 



When the walls of the filamentous branches swell, their cell content 

 is reduced to a mere granular thread except at the very apex, though 

 earlier a well-marked prolongation of the protoplast with normal proto- 

 plasmic appearance extended to the end of each branch. With the 

 swelling of the wall this structure gradually deteriorates, though a gran- 

 ular thread persists till a late stage to mark the original lumen of the 

 branch. At the very apex the wall does not swell so strongly and the 

 protoplast also persists as a small oval vesicle tapering below into the 

 granular thread just mentioned (fig. 51). As a result the upper ends 

 of the filaments are slightly enlarged and the surface of the slime mass 



