204 DISEASES OF CULTIVATED PLANTS 



strands closely adpressed to the surface of the leaf. Nestling 

 amongst this felt of mycelium are the numerous, very minute 

 black perithecia, which contain small, hyaline, cylindrical 

 conidia, 8-ioXi"5-2 /jl. The ascospore form occurs on the 

 dead leaves in the spring following their fall. Perithecia 

 immersed, with a long, stout beak projecting from the under- 

 surface of the dead leaf; asci 60-80 X 5-6 jx; 8-spored ; spores 

 hyaline, needle-shaped, often slightly bent, with one central 

 septum, 43-54 x 1 11. 



Klebahn, Zeitschr. Pflanzenkr., 18, p. 129 (1908). 



Walnut leaf blotch. Brown patches are not uncommon 

 on living leaves of Juglans rcgia. Such spots, unless present 

 in large numbers, do very little harm, but when an epidemic 

 occurs the leaves fall early in the season. Until quite recently 

 Marssonia juglandis (Sacc), considered as an entity, was held 

 responsible for the injury caused, but Klebahn has shown 

 that Marssonia is only the conidial condition of an ascigerous 

 fungus named Gnomonia leptostyla (Ces. and de Not.). The 

 ascigerous form is produced on dead ; fallen leaves in the 

 spring, 



Marssonia form. The conidial fruit forms small black 

 specks situated on large brown or greyish-brown patches on 

 the leaves. Conidia fusiform, usually curved, i-septate, 

 hyaline, 14-26x2-3 /*, springing from the tips of short conidio 

 phoi 



A second form of conidia are produced from the same 

 spots; fusiform, hyaline, continuous, 6-i2Xi-i'5 /*. 



Ascigerous form. Perithecia globose, with a long, project- 

 ing beak: asci cylindric-clavate, 8-spored; spores cylindric- 

 fusiform, hyaline, I -septate, 19 25 X 2*5-3 /i. 



Spray with Bordeaux mixture when the leaves arc young. 

 Collect and burn fallen leaves. 



Klebahn, Zeitschr. Pflanzenkr.^ 17, |>. 223 (1908). 



VENTURIA. (De Not. and ClS.) 



Perithelia subsuperficial, often setulose ; asci 8-spored: 

 paraphyses absent; spores elongated, uni-septate, yellowish. 



Apple scab. Undoubtedly the most injurious fungus 

 attacking the apple-tree, in many instances rendering unsale- 



