38 PEACH LEAF CURL". ITS NATURE AND TREATMENT. 



In view of these facts, it seems possible that the ascogenous cells 

 may be capable of enduring-, under especially favorable conditions, a 

 resting period of considerable time. Such resting ascogenous cells 

 have been sought for upon the swollen branches of the peach, how- 

 ever, without success. Further research along this line is desirable. 

 As the fungus is already known to fruit upon the blade and petiole 

 of the leaf and upon the blossom, and a vegetative mycelium is found 

 growing thriftily in the swollen branches, there seems to be no good 

 reason why the parasite may not fruit upon the infected twigs. 



The perpendicular growth of the developing asci in the leaf soon rup- 

 tures or pierces the cuticle, and where large numbers of asci develop 

 at the same time the cuticle is lifted, torn, and lost, the asci forming 

 a more or less continuous plush-like surface growth. Isolated asci 

 press through the cuticle so as to form separate perforations (PL III, 

 fig. 21). The contents of the forming ascus are finely granular, and 

 as the ascus elongates these contents crowd into the upper portion and 

 a septum is formed across the basal part in such a manner as to cut off 

 the now emptied ascogenous cell as a stalk cell for the ascus (PI. Ill, 

 fig. 15), When fully developed the asci are usuall}^ broader at the top 

 than at the base, and often somewhat clavate in form. A series of asci 

 measured varied in length from 34 to 4-1 yw, the average being 38 f^ ; the 

 width of the asci ranged from 10 to 12 yu, and the height of the stalk 

 cells varied from 8 to 13 /<, the average being slightly over 10 ^ (PI. 

 Ill, figs. 1-13). 



The formation of the ascospores in Exoaseus deformans has not been 

 carefully studied Ijy the writer. Sadebeck has shown, however, for E. 

 turgidus^ that mitotic nuclear division occurs in the ascus in connec- 

 tion with spore formation (Untersuch. tiber die Pilzgattung Exoas- 

 eus, Hamburg, 1884, PI. Ill, fig. 20). The ascospores developed in 

 the asci of E. deformans vary in number from 3 to 8, the latter being 

 the full and typical iumi])er. When mature they are surrounded by a 

 moderately firm cellulose wall, which is rather inconspicuous, owing 

 to its transparency. The spores are usually somewhat oval in form, 

 being longer than broad, but occasionally some are seen which appear 

 nearly or quite spherical. Fresh ascospores sometimes show distinct 

 nuclear phenomena. This has been oljserved with spores still within 

 the ascus, as well as in many which have escaped. The nucleated 

 appearance seems less common in budding or germinating ascospores 

 than in those in a resting condition (PI. IV, figs. 1, 2, 3, 4, and 10). 

 The average length of the ascospores measured was TyV /^,. the length 

 varying from 6 to 9 yu, and the average width was 6t\ a*, varying from 

 5 to 7 yw. The ascospores escape from the ascus through an apical rup- 

 ture of the latter. 



Germination of the ascospores has been observed by the writer to 

 proceed in two ways: (1) By means of budding oi- conidia formation; 

 (2) by means of stocky germ tul)es, often one branched and resembling 

 promycelia. 



