4 BULLETIN 360, U. S. DEPAKTMENT OF AGKICULTUKE. 



infection; badly stunted yellow pine, larch, Douglas fir, and lodge- 

 pole pine growing in the open and on otherwise good sites often 

 measure less than 6 inches at the stump, but show ages ranging from 

 100 to 200 years or more. Young seedlings, if not killed outright 

 within a comparatively short time after infection, usually show a 



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FIG. 2. Graphs showing the average annual growth (in inches) for 40 years (1874 

 to 1913, inclusive) of 50 trees of yellow pine heavily infected with mistletoe, com- 

 pared with 50 uninfected trees of the same species for the same period. A, heavily 

 infected trees : Average-age class, 100 years ; average height, 49.5 feet ; average 

 diameter, breast high, 18.2 inches. B, Uninfected trees : Average-age class, 100 

 years ; average height, 77.2 feet ; average diameter, breast high, 22 inches. 



marked falling off of the foliar surface of the parts uninfected and 

 finally succumb to the attack (fig. 5). Very frequently young in- 

 fected seedlings develop into ball-like brooms. 



Table II shows the youngest age class of five hosts at which mistle- 

 toe infection has been found to occur and the locality where the 

 observations were made. 



