DlE-i)ACK Oi'" Al'i'Ll-. TRI-IES. 547 



The genus has thus been reported from all the four Pro- 

 viaices of the Union, but it cannot be said that it has thus far 

 caused a general epidemic. Wherever it is found it is con- 

 sidered a most serious pest, against which little can be done. 

 One farmer said : " This is the most serious disease I have on" 

 my farm." 



The present investigation was undertaken j^rimarily to in- 

 vestigate further the parasitic nature of the fungus, and to carry- 

 out cross-inoculations. The fungus here described was isolated 

 from a diseased apple branch. Recently it has also been isolated 

 from a peach branch, and a comparative study of the two is 

 now in progress. During the season it is hoped to obtain cross- 

 inoculations with fungi from these two hosts, and thus further 

 to study the life-history and parasitism of the genus. 



The following appear to be synonyms of C. leucostoma : — 



Sphceria leucostoma (Pers. Syn., page 39). 

 Valsa Pcrsoonii (Nits. Pers. Germ., p. 222).* 

 Valsa leucostoma (Fr. Surnm. Veg. Soc, p. 141).* 



The Disease. 



Symptoms. — This disease, as observed in apple trees in 

 South Africa, frequently shows at the trunk of the tree near 

 the ground as a coiTee-coloured discoloration, and from here 

 spreads upwards. The trees die outright, usually the second 

 summer after they are attacked. On the trunk canker wounds, 

 resembling those caused by Diplodia psciidodiplodia Del., are 

 frequently formed. f 



Specimens of diseased twigs have also been submitted for 

 examination, and there can be no doubt that as well as 

 attacking the trunks the disease may also start on the branches 

 and spread downwards, this producing a condition which has 

 frequently been observed on peach trees in this country, vis., 

 a die-back of the branches, accompanied by a curling and yellow- 

 ing of the leaves of infected branches. The skin of diseased 

 branches is decidedly leathery, and in later stages becomes loose 

 and wrinkled. The colour varies from a lightish purple tint to 

 a black purple. The entire dead portions later become dotted 

 over with the black, silvery-capped pustules of the fungus. 

 These pustules form below the epidermis, gradually enlarge, and 

 finally break through a transverse slit in the epidermis, and 

 appear as having a white disc-like cap (Plate 20, a and h). Dead 

 twigs 14 inches long had these pustules throughout their entire 

 length. 



A branch with numerous pustules was placed in distilled 

 water in a moist atmosphere, and soon the spores of the fungus 

 issued out as chocolate-brown curls. Blackish pycnidia breaking 

 through a transverse slit were also observed (Plate 20, c). 



* Sacc. 1, 139. 



t " Observations in the Field," by Mr. P. J. Pienaar. 



