Pathogenicity of the Chestnut Bark Disease 57 



room temperature germinated four months after collection., Three 

 weeks later they could not be induced to germinate. Material- 

 exposed out of doors and that kept moist and at about 24 C. in 

 a greenhouse failed to give germination of conidia after one 

 month ; earlier tests not having been made. Conidia hung in 

 cheese cloth in the trees for two weeks would not germinate. 

 Conidia from bark kept dry for two weeks would not germinate. 

 Conidia in moist soil retained their viability for 11 weeks. It 

 is evident that viable conidia are usually present in the soil be- 

 neath infected trees and are subject to transportation with the 

 soil, mud, or dust. 



In the laboratory the ascospores showed greater vitality 

 than the conidia. They germinated in distilled, tap, and rain 

 water, while the conidia appeared to germinate only in the rain 

 water. Again these results can only be regarded as indications 

 of vitality, as tests showed later that the rain water used was 

 slightly acid, the tap water alkaline to phenolphthalein, and the 

 distilled water showed traces of copper. In the same experi- 

 ment it was found that conidia grown in winter had less possi- 

 bility of growth than those produced by the pycnidia in summer. 

 Conidia taken from the fungus which had grown on artificial 

 media for 8 months and 13 days were capable of germination. 

 The mycelium of a test-tube culture 9 months old was still cap- 

 able of renewed growth when transferred to a Petri dish con- 

 taining sterile agar. 



Vitality and longevity tests were made in April, 1912, with 

 an infected piece of chestnut branch, collected in Monroe County, 

 Pa., in July, 1908, and continuously kept in a damp chamber at 

 the Department of Forestry at Harrisburg since that date. The 

 bottom of a damp chamber was rilled with water and the speci- 

 men was suspended above the water. The fungus made a small 

 growth, but after it had produced a small number of pycnidia 

 growth ceased. The conidia when cultured were found to ger- 

 minate. They in turn made a small growth but were unable to 

 produce any fruiting pycnidia. A small portion of the bark was 

 removed from the specimen and placed in another damp cham- 

 ber. This specimen produced no growth whatever. This shows 

 that at the end of 45 months the fungus had almost completely 

 lost its vitality. It is barely possible that this loss of vitality may 

 have been hastened slightly by the growth of Penicillium which 

 partially covered the surface of the specimen. 



Bark permeated with the mycelium which had not been ex- 

 posed to cold or thoroughly dried on being placed in from 19 

 to 24 C. temperature and a saturated atmosphere abundantly 



