20 



BULLETIN 658, U. S. DEPARTMENT OF AGRICULTURE. 



pathology. This is noticeable in the work done in the study of the 

 chestnut -blight fungus 1 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, 3 J 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. II. Field studies on the Endothia canker of chestnut in New York State. 

 Fhytopathology, v. 4, no. 4, p. 237. 1914. 



2 Spauldrng, Perley. The blister rust of white pine. U. S. Dept. Agr., Bur. Plant Indus. 

 Bui. 200, 88 p., 2 pi. (1 colored). 1911. Bibliography, p. 61-78. Map showing 

 distribution of blister rust in Europe, p. 14. 



Ilcdgcock, G. G., and Long, W. H. A disease of pines caused by Cronartium pyri- 

 forme. U. S. Dept. Agr. Bui. 247, 20 p. 1915. Literature cited, p. 20. Map showing 

 distribution of Cronartium pyriforme, p. 8. 



