54 

 DEVELOPMENT IN SAPWOOD AND HEARTWOOD. 



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

 atmosphere constantly, an abnndant development of pycnidial 

 fruit bodies was noted in about two months from both sapwood 

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

 velopment in wood shattered by lightning has beeu mentioned 

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

 lied shoots; in both cjises, the i)ai-(s liad been distinctly iiijnrcMl 

 by insects. 



SUMMARY OF FIELD STUDIES AT OKP.ISONLV, PA. 



During the fall and early winter of l!ill-ll', Mr. li. 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-Uve years 

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

 of the chestnut growth was coppice of four years standing. 

 Ilather severe tire injury had occurred in 11)02, and the land had 

 been pastured recently. Soil conditions and density of stand 

 varied considerably over the tract. The infection was 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 cliestnut trees, 

 sprouts, and stumps were examined and t\yo liundred and eighty, 

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

 all were four year coppice growth. The oldest lesions wpre 

 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 tl»at 

 153 trees in southeastern Pennsylvania, near ITaverford exi)()sed 

 to natural infection, carefully examined aiui marked as unin- 

 fected in J.ninary 1911, showed 25 trees infected in a recent ex- 

 amination. This would indicate something, perliaps, of the 

 rapidity of the spread ol the disease, wliere observations were 

 made upon that point. 



