14 



BULLETIN 317, U. S. DEPARTMENT OP AGRICULTURE. 



Table I. — Extent and nature of mistletoe infection in 36 larch trees in the 

 Whitman National Forest. 





Breast- 

 high 



diam- 

 eter. 



Height 

 of • 

 tree. 



Number of burls. 



Number of witches '-brooms. 



Gen- 

 eral 



vigor 

 of 



tree. 



Gen- 

 eral 



Tree No. 



On 



trunk. 



At base 



of 

 branches. 



At base 



of 

 branches. 



On 



branches. 



Total 

 on 

 tree. 



Fallen 

 from 

 tree. 



mer- 

 chant- 

 able 

 condi- 

 tion. 



12 



Inches. 

 7 

 7 

 9 



10 

 11 

 12 

 12 

 13 

 14 

 14 

 15 

 15 

 15 

 16 

 17 

 " 17 

 17 

 18 

 18 

 18 

 19 

 20 

 20 

 20 

 22 

 23 

 23 

 23 

 24 

 25 

 28 

 28 

 28 

 29 

 29 

 30 



Feet. 

 51 

 68 

 75 

 50 

 85 

 64 

 66 

 95 

 78 

 122 

 98 

 84 

 83 

 88 

 85 

 88 

 90 

 99 

 103 

 80 

 99 

 103 

 120 

 109 

 107 

 100 

 110 

 109 

 110 

 111 

 126 

 110 

 119 

 123 

 125 

 120 



1 



1 

 

 

 

 

 

 

 

 



1 





 



1 





 2 

 



1 







1 







1 





 3 

 1 

 2 

 3 

 4 

 1 

 2 

 

 1 

 3 

 3 

 

 



4 

 4 

 

 

 2 

 

 

 

 

 

 

 3 

 

 2 

 4 

 8 

 1 

 

 

 1 

 

 2 

 3 

 4 

 1 

 4 

 6 

 2 

 2 

 3 

 

 2 

 1 

 4 

 14 

 3 



5 

 6 

 

 

 2 

 4 

 3 

 6 

 

 

 4 

 4 

 

 4 

 5 

 4 

 2 

 3 

 

 3 

 

 4 

 3 

 3 

 3 

 8 

 5 

 1 

 3 

 4 

 

 1 

 2 

 6 

 5 

 2 



13 



10 







18 



12 



15 



16 



12 











8 



15 







20 



15 



20 



11 



8 







5 







18 

 20 

 21 

 10 

 8 

 16 

 10 

 15 

 10 

 

 10 

 20 

 10 

 20 

 6 



18 

 16 

 

 18 

 14 

 19 

 19 

 18 

 

 



12 



19 







24 



20 



24 



13 



11 







8 







21 



23 



23 



13 



16 



21 



11 



18 



14 







11 



22 



16 



25 



8 



1 

 1 

 

 1 

 1 

 2 

 

 2 

 

 

 2 

 3 

 

 3 

 17 

 3 

 1 

 1 

 

 3 

 

 4 

 6 

 4 

 

 9 

 7 

 1 

 4 

 4 

 

 2 

 2 

 2 

 6 

 



Poor. . 





16 



...do... 



Good.. 



Fair... 

 ...do... 

 ...do... 

 ...do... 

 ...do... 



Good.. 

 ...do... 



Fair.. 

 ...do... 



Good.. 



Poor.. 

 ...do... 

 ...do... 

 ...do... 



Fair... 



Good.. 



Fair... 



Good.. 



Fair... 

 ...do... 

 ...do... 

 ...do... 



Poor.. 

 ...do... 

 ...do... 



Fair... 



Poor.. 



Good.. 



Fair... 



Poor.. 

 ...do... 

 ...do... 



Fair... 





15 



Good. 



29 



Do. 



11 



Do. 



9 



Do. 



10 



Do. 



14 





7 



Good. 



20 



Do. 



5 





13 



Do. 



17 



Good. 



18 





1 



Do. 



21 



Do. 



22 



Good. 



19 



Do. 



25 



Do. 



33 



Do. 



2 



Do. 



23 





24 



Do. 



26 



Do. 



8 



Good. 



3 



Fair. 



6 





32 



Do. 



30 





36 





27 



Good. 



28 



Do. 



31 



Poor. 



35 



Do. 



4 



Do. 



34 



Fair. 







Owing to the slower growth of the branches in length as compared 

 to the stem, the cortical roots of the mistletoe are enabled to extend 

 into the older part of the 2-year-old internodes. After a time the 

 branch is suppressed and the terminal bud becomes infected, resulting 

 in a terminal broom. The cortical roots likewise penetrate the foliar 

 spurs, causing them to become greatly enlarged, with the result that 

 few leaves are produced (fig. 12). It is remarkable how rapidly in 

 some instances the burl tissues become differentiated. A slight swell- 

 ing is first noticeable ; then the bark begins to lose its fresh appear- 

 ance, becomes rough around the edges of the infected tissues, and 

 finally separates altogether from the normal bark (fig. 11). The 

 vertical roots of the parasite continue to live for many years, elon- 

 gating with the same rapidity with which the annual increment of 

 the host is laid down. The hypertrophied tissues resulting from these 

 early infections on the stem spread out in fanlike shapes when 

 viewed in cross section (figs. 8 and 10). Original infections on 

 branches not only cause a local hypertrophy of the immediately 



