THE FRinTINO HAHITS OK THE FUNGI'S. 37 



sprnid out Ix-l wci'ii (lie cpidci'iiial cells ol" (lie leal' and {\\r ciiti- 

 flc tlii'y arc iiuich distorted, curved, and lohed, tlic lu'unches and 

 lol»os pvontuaily tillini;. in a (luite uiiiforni and continuous manner, the 

 entire space between the elevated cuticle and epidermis, so that a 

 more Ol" less pcrl'ect and continuous hymenial layer of ascoocnous 

 cells is formed (PI. II. ti^-. •>; 1>|. HI. ri«rs. 23, 24, 25, 2(), and 27). At 

 this time the cells become well rounded and heavy-walled, and they 

 may or may not become loosened and separated from each othiM* 

 (PI. 111. ti<js. 28-80). These are now the fully developed ascooe- 

 nous cells of the hymenium. and they are fully stored with nutritive 

 materials for the development of the asci. In their compact, continu- 

 ous, jind rounded condition they resemble, when viewed from the sur- 

 face, the stones in the pavement of an old Roman hiujiway. 



The various phases of the development of the hymenium of ascog- 

 enous cells may often be observed at one time in a single infected 

 leaf. The center of a swollen spot frecpiently shows the fully devel- 

 oped hymenium, while at the margin of the spot the first filamentous 

 hyi)ha' are just spreading beneath the cuticle. In such instances 

 nearly all stages in the develo})ment of the ascogenous cells may be 

 studied in a single well-prepared specimen. The development of a 

 subcuticular hymenium has been observed in the petiole as well as in 

 the blade of the leaf. 



The formation of the asci from the fully developed ascogenous cells 

 has been carefully followed in the stud}' of a large number of prepara- 

 tions. Thus far no sexual phenomena have been observed in connec- 

 tion with the formation of the ascogenous cells or with the develop- 

 ment of the asci. As already said, the walls of the ascogenous cells 

 are heavy. The early steps in the development of the asci from these 

 cells (the development of a papilla-like elevation on the upper surface 

 of the cells) cause the rupture or dissolution of the heavy wall where 

 the elevation occurs. The phenomenon is that of the germination of 

 a heavy-walled spore, or, perhaps, more properly, the outgrowth or 

 prolongation of an endospore through the rupture of the epispore 

 (PI. Ill, figs. IT, 18, etc.). The fact to be noted is the perfect rest- 

 ing condition into which the ascogenous cells may pass before the 

 development of the ascus, as shown by the marked delimitation between 

 the thin wall of the forming ascus and the heavy wall of the ascogenous 

 cell. The entire isolation of single ascogenous cells or groups of cells 

 from all sources of vegetative supply indicates that the ascus is 

 entirely dependent for its nourishment upon the stored materials of 

 the cell from which it arises. The pushing of the ascus after the com- 

 plete development of the ascogenous cell instead of in direct con- 

 tinuation of the development of the latter, also points to a proba})le 

 cessation and renewal of the reproductive activity of the ascogenous 

 cell. 



