54 



DEVELOPMENT IN SAPWOOD AND HEARTWOOD. 



Where a section of a large infected branch was kept in a moist 

 atmosphere constantly, an abundant development of pycnidial 

 fruit bodies was noted in about tAvo months from both sapwood 

 and heartwood at the more moist cut surface. The similar de- 

 velopment in wood shattered by lightning lias been mentioned 

 above. In two cases, the fungus was found on young, unligni- 

 fied shoots; in both cases, the parts had been distinctly injured 

 by insects. 



SUMMARY OF FIELD STUDIES AT ORBISONIA, PA. 



During the fall and early winter of 1911-12, Mr. R. C. Walton 

 made a detailed study of an advance spot of infection at Orbi- 

 sonia, Huntingdon county, in Central Pennsylvania. The tract 

 covered some forty-six acres on the north and northwest slope of 

 a mountain. It had been cut over originally forty-five years 

 ago, and at intervals since, the last cutting being in 1908. Most 

 of the chestnut growth was coppice of four years standing. 

 Rather severe fire injury had occurred in 1902, and the land had 

 been pastured recently. Soil conditions and density of stand 

 varied considerably over the tract. The infection Avas found in 

 detached spots over about thirteen acres. There was one spot 

 that seemed to be the original centre of infection, dating back 

 two years ; but elsewhere in the area there were lesions apparently 

 as old. Altogether three thousand and fifty-nine chestnut trees, 

 sprouts, and stumps were examined and two hundred and eighty, 

 or 9.1 per cent, were found to be infected. Of these, practically 

 all were four year coppice growth. The oldest lesions were 

 seemingly two years old, and ten of these were found. The 

 youngest were for the current season, and of the total, about half 

 seemed to be less than one year old ; and estimates of the age of 

 all the lesions indicated a very uniform rate of spread during 

 the two years. It may be added from a recent investigation that 

 153 trees in southeastern Pennsylvania, near Haverford exposed 

 to natural infection, carefully examined and marked as un in- 

 fected in January 1911, showed 25 trees infected in a recent ex- 

 amination. This would indicate something, perhaps, of the 

 rapidity of the spread ol the disease, where observations were 

 made upon that point. 



