170 Bulletin 395 



Shortly after the stroma begins to develop, conidiophores arise, usually 

 in groups over the surface, and these bear conidia. The conidia are 

 embedded in a gelatinous substance which is soluble in water, and there- 

 fore they may be splashed by rain to the surrounding canes. According 

 to Appel (191 5), this gelatinous substance which covers the spores also 

 aids them in sticking to the heavy wax cuticle of the raspberry cane. 



The conidia germinate wnthin a period of from three to twelve hours in 

 water and on various nutrient media, but the writer has never obsen-ed 

 more than a forty-per-cent germination. From the few observations made 

 their vitality appears to be short, although Scribner (1888) was able to 

 germinate spores that had been kept in the herbarium for several 

 months. Drying the conidia on a glass slide for twenty-four hours does 

 not injure their vitality, but repeated drying causes their death. 



It is possible that the fungus dies after the production of conidia in the 

 spring, since the writer has found but few conidia in old lesions after early 

 summer and these were evidently left from the early production. Further- 

 more, spores were never produced when diseased canes that had borne 

 fruit were placed in moist chambers, and the writer has never been able to 

 obtain cultures of the fungus from plantings of such tissue. The death of 

 the pathogene cannot be attributed to the dying of the host after fruiting 

 time, as the fungus on one-year-old canes which have winterkilled may 

 produce conidia in great abundance the following spring. Here it should 

 be remembered that, although raspberry roots are perennial, the canes are 

 biennial. The fungus living on the latter has a similar life period, even 

 though it is not entirely parasitic on its host. 



PATHOLOGICAL HISTOLOGY 



Very little has been done by previous investigators on the pathological 

 histology of raspberry affected with anthracnose. Scribner (1888) states 

 that " the greatest injury is confined to the cambium layer, or the portion 

 through which the sap is conveyed in the process of growth." Paddock 

 (1897) states that " it is not known that the fungus works into the wood 

 but its attacks occasionally cause the canes to crack and expose the pith." 

 As to the exact tissues invaded by the fungus and the various pathological 

 conditions which arise in them, nothing has been written. 



The following observ^ations were made on diseased canes of the Colum- 

 bian variety of raspberry. This is a purple-cane variety and possibly is 

 more severely attacked by the fungus than are any of the blackcap varieties. 

 The lesions frequently develop to a greater extent on the former than on 

 the latter, and thus a wider range of stages may be observed. 



Infection takes place more readily on young and tender canes, and 



throughout the summer the small reddish purple spots indicating recent 



2Sr 



