ASCOMYCETES 



213 



3. The perithecia bearing the ascospores are relatively simple. 

 The asci are evanescent, and the spores unicellular, lenticular, 

 vacuolate, and measure about 12 x 5 p. 



Artificial cultures are readily made on various media, and 

 the first two spore stages may be quickly produced in culture, 

 the endospores, particularly, being aerial. The association of the 

 ascosporous stage with the others and the apparent continuity 

 of mycelium are believed to show genetic connection. 



Control. Since the seed bed is perhaps the greater source 

 of trouble in the case of tobacco, sterilization of the soil where 

 the disease has become established may be necessary. Diseased 

 plants should not be used for planting. Thorough aeration of 

 the soil by drainage and cultivation is also desirable. The sug- 

 gestion that this fungus is constantly associated with an 'alkaline 

 soil requires an investigation of the soil conditions with a view to 

 correcting this by subsequent fertilization. 



XX. SOOTY MOLD OF ORANGE 

 Meliola Camellia (Catt.) Sacc. 



FARLOW, W. G. On a Disease of Olive and Orange Trees, occurring in Cali- 

 fornia in the Spring and Summer of 1895. Built, of the Bussey Institu- 

 tion 5 : 404-414. 1876. 



WEBBER, H. J. Sooty Mold of the Orange and Its Treatment. Div. Veg. 

 Phys. and Path., U. S. Dept. Agl. Built. 13: 1-34. pis. /-j. 1897. 



Distribution and effects. The sooty mold is a disease which is 

 probably distributed throughout all moist citrus-growing regions. 

 It is perhaps most injurious upon the orange, but it occurs also 

 upon the other cultivated citrous fruits. In one sense it is scarcely 

 to be regarded as a fungous disease, since the fungus which pro- 

 duces the obnoxious effect is probably not parasitic. Nevertheless, 

 the fruit infested by the sooty mold is seriously injured from the 

 commercial standpoint, and since it is the fungus which effects 

 this injury, it may justly be considered in this connection. 



The sooty mold consists, as the name implies, of a sooty 

 growth, or crust, which occurs both upon leaves and fruit. It 

 may appear in isolated patches or investing practically the entire 

 leaf or fruit surface. The black mass is made up entirely of 

 fungous hyphae. The fungus is only found following the attack 



