20 BULLETIN 658, U. S. DEPARTMENT OF AGRICULTURE. 
pathology. This is noticeable in the work done inthe study of the 
chestnut-blight fungus? and in the study of two of our important 
forest-tree rusts.2 These are all maps of the plain black-and-white 
type, showing by means of symbols the localities where infection 
was reported and thus indicating the distribution of the disease. 
The earliest colored maps used in forest-disease investigations are 
found in German literature and deal mainly with the distribution of 
zones of timber damaged by smelter fumes. 
Fig. 20.—Mistletoe burl affecting one side of larch log. Size of burl, 33 feet long by 
13 inches in diameter. The cull equaled 25 feet board measure. 
Colored maps giving the distribution of smelter-smoke damage 
were published in a book on smoke damage to vegetation by 
1 Rankin, W. H. Field studies on the Endothia canker of chestnut in New York State. 
Phytopathology, v. 4, no. 4, p. 237. 1914. 
* Spaulding, Perley. The blister rust of white pine. U.S. Dept. Agr., Bur. Plant Indus. 
Bul. 206, 88 p., 2 pl. (1 colored). 1911. Bibliography, p. 61-78. ‘Map showing 
distribution of blister rust in Europe, p. 14. 
Hedgecock, G. G., and Long, W. H. A disease of pines caused by Cronartium pyri- 
forme. U.S. Dept. Agr. Bul. 247, 20 p. 1915. Literature cited, p. 20. Map showing 
distribution of Cronartium pyriforme, p. 8. 
