8 



BULLETIN 1112, U. S. DEPARTMENT OF AGRICULTURE. 



and at every 8 feet above this point. The measurements were 

 recorded by 5-year periods instead of by decades, as is. the usual prac- 

 tice in complete stem analysis. The trees were selected as nearly as 

 possible from the same site, kind of stand, and the same age and 

 crown classes. Only those trees free from abnormalities or other 

 possible causes of deterioration or conditions deterrent to their 

 growth were studied, thus permitting only two variables to enter 

 into the results, the age of the tree and the degree of mistletoe infec- 

 tion. The classification of the tree according to degree of infection 

 represents the consensus of opinion of three different observers. 



The basic data for each of the individual felled trees which were 

 analyzed to show the effect of mistletoe on th-e growth and seed pro- 

 duction of western yellow pine have been arranged in Table 7, accord- 

 ing to the age of the trees. In compiling the stem analyses the data 

 for each tree were computed separately. The diameters and heights 

 of each tree for each fifth year, dating back from the year of analysis, 

 were correlated with age in growth-analysis diagrams, from which 

 the dimensipns of each tree for each integral 5 years of age or quin- 

 quennium were read. 



Table 5. — Companson of the average diameter growth or accretion of S3 standing black 

 jachs, for a 5-year period, at 4-5, 17, and 33 feet from ground, grouped according to 

 degree of mistletoe infection. 





Diameter outside bark. 



Accretion, 1911-1916. 





Degree of 

 infection. 



1911 



1916 



Periodic. 



Periodic annual. 



Basis. 





4.5 

 feet. 



17 



feet. 



33 



feet. 



4.5 



feet. 



17 

 feet. 



33 

 feet. 



4.5 

 feet. 



17 

 feet. 



33 

 feet. 



4.5 

 feet. 



17 

 feet. 



33 

 feet. 









In. 

 17.93 

 22.25 

 15.92* 

 16.47 



In. 

 16.28 

 19.59 

 13.20 

 14.42 



In. 



12.69 



14.14 



8.65 



9.19 



In. 

 19.03 

 23.40 

 16.78 

 17.15 



In. 

 16.30 

 20.85 

 13.81 

 14.64 



In. 

 13.71 

 15.25 

 9.46 

 9.31 



In. 



1.10 



1.15 



.86 



.68 



In. 



1.02 



1.26 



.61 



.22 



In. 



1.02 



1.11 



.81 



.12 



In. 



0.22 

 .23 

 .17 

 .14 



In. 



0.20 

 .25 

 .12 

 .04 



In. 

 0.20 

 .22 

 .16 

 .02 



Trees. 

 16 



X 



4 



XX 



7 



XXX 



6 







Table 6. — Comparison of the total volume growth or increment of 33 standing black 

 jacks, for a 5-year period, grouped according to degree of mistletoe infection. 



Degree of infection. 



Total volume. 



Increment, 1911-1916. 



Basis. 



1911 



1916 



Periodic. 



Periodic annual. 





Cubicfeet. 

 919. 76 

 359. 07 

 286.83 

 262.65 



Cubicfeet. 



1,047.40 



410. 65 



316.08 



273.97 



Cubicfeet. 

 127.64 

 51.58 

 29.25 

 11.32 



Cubicfeet. 

 25.53 

 10.32 

 5.85 

 2.26 



Per cent. 

 2.78 

 2.87 

 2.04 

 .86 



Trees. 



16 



X 



4 



XX 



7 



XXX 



6 







