398 



SCIENCE 



[N. S. Vol. XXXIV. No. 874 



fungus infects only the cambium of the bark 

 and that the mycelium did not enter the cam- 

 bium of the wood. During the survey just 

 referred to, one well-defined instance was 

 found where yellow pustules, plump and vigor- 

 ous, were growing upon freshly exposed wood. 



In this region the beginning of infection in 

 a large number of cases was at a single point 

 in the crown and in a few brown pustules in 

 the deep cracks at the base of the tree. An 

 exposed root running out horizontally for a 

 foot or more was almost sure to contain pus- 

 tules, no doubt washed down the stem by the 

 rains, or brought by drip from neighboring 

 trees with infected branches. 



The appearance of the bark of a tree after 

 an attack from this fungus is extremely char- 

 acteristic. The bark will split, the surface 

 within the lesion shows a sulphury-yellow tint, 

 while numerous brown but minute wart-like 

 excrescences will be found upon the unbroken 

 bark surface. In the deep old bark cracks, it 

 takes the appearance of reddish or orange- 

 colored lines. The tendency of the disease is 

 to encircle the branch or trunk. This pro- 

 duces another well-known mark, a depression 

 or apparent sinking of the affected bark. In 

 reality this is caused by the tree rushing 

 nutriment to the spot and depositing it at the 

 edges of the infected area, circulation being 

 cut off within. 



Another noteworthy fact respecting the life 

 of this fungus is its great vitality. Unbarked 

 chestnut rails made into fence and apparently 

 well dried for a year or more have been found 

 to contain active friiiting bodies. A pile of 

 fence rails containing bark which was decayed 

 to the point of falling from the wood by its 

 own weight carried the blight in vigorous 

 condition after two years. A specimen con- 

 tained in a moist cell was found to be pro- 

 ducing pustules after thirty-seven months. 

 Just what amount of vitality wiU be retained 

 by the dried spores and for how long is not 

 definitely known. Certain it is, however, that 

 the life within it is of unusual persistency and 

 must be dealt with from that view point. 



Prior to the year 1908 the chestnut bark 

 disease was almost unknown in Pennsylvania. 



In the latter part of that year and in the early 

 part of 1909, the attention of the Pennsyl- 

 vania Department of Forestry was directed to 

 its threatened invasion, by Dr. John Mickle- 

 borough, of Brooklyn, N. Y. Dr. Micklebor- 

 ough pointed out the fact that the disease had 

 probably entered the state and would continue 

 its course westward were it not checked; also 

 that it would be desirable to know to what ex- 

 tent it had entered Pennsylvania. Accord- 

 ingly, the Deputy Commissioner of Forestry 

 was detailed to accompany Dr. Mickleborough 

 on a tour of inspection to determine the limits 

 of the disease. This work was begun in the 

 latter part of March, 1909, and was continued 

 throughout that month and during the month 

 of April, in which time many localities were 

 examined. All of the southeastern counties 

 of the state were inspected. At this time it 

 was found that the main body of the disease 

 was confined to the southeastern corner and 

 that it had not crossed the north branch or the 

 main river Susquehanna, except in the two 

 instances discovered by the U. S. Department 

 of Agriculture. Following this inspection, a 

 report was prepared and printed, illustrated 

 with drawings of the fungus in detail and 

 accompanied by a print made by color pho- 

 tography, showing the appearance of the dis- 

 ease on living bark when developed to its full- 

 est growth. Beside the articles appearing in 

 botanical periodicals and the early reports of 

 the U. S. Department of Agriculture, this 

 report was the first to cover in detail any por- 

 tion of country and the first report to be is- 

 sued on the subject by any one of the states. 

 Thus, within a short period, the disease devel- 

 oped from something unknown to a very de- 

 cided and prominent attack upon one of the 

 important wild trees of the commonwealth, 

 and was rapidly extending itself to the west- 

 ern counties. 



Somewhat prior to this time the officials of 

 the Office of Forest Pathology in the U. S. De- 

 partment of Agriculture were concerning 

 themselves with its appearance in and around 

 the city of Washington. They found it there 

 rather numerously, and immediately applied 

 the heroic remedy of cutting out and destroy- 



