22 BULLETIN 1112, U. S. DEPARTMENT OF AGRICULTURE. 
TABLE 16.—The effects of mistletoe on the photosynthetic surface of western yel 
pine—Continued. 
Leaf surface. : 
Totalntin-| 2 ¢. (jee oe Se 2 ee ES, to 
iPrde Mo ber ofleaves ; Ratio ofleaf} Ratio of 4 
‘ Soe in entire Lower Central Upper Entire surfaces. | volumes.! } 
crown. portion of | portion of | portion of crown. 
crown. crown. crown. % 
BAe eee) coer Oe Co ie a) GSTS a eae Reet 
Square Square Square Square 
inches. inches. inches. inches. 
10S es. Se , 543 4,094.1 19, 400.4 32, 348.2 55, 842.7 1.0 “TQ 
1 (Ue eee OS 1,792,439 | 217,828.8 | 356,549.8 | 231,613.4 | 805, 992.0 14.4 7.6 
i) Gee TE ae 262, 015 40, 910.5 , 983.9 44, 427.4 | 110,321.8 2.0 1.4 
11 ene ae serene art 7,09 218, 438.4 | 198,228.7 | 128,939.5 | 545, 606.6 9.8 9.0 
ROT eee eee 419, 774 50, 960. 3 | 105, 868.9 | 107,921.4 | 264, 750.6 4.7 . 96 
1 In these ratios Tree No. 103 is taken as unity. 
The average length and width of the leaves in the 10 tufts selected 
were used in determining the leaf surface for a given section of the 
crown, and this in turn for finding the total leaf surface of a given 
tree. Table 16 shows that not only does the mistletoe shorten the 
length of both leaf tufts and leaves, but it also materially decreases the 
number of leaf tufts per tree for heavily infected trees when compared 
with healthy trees of the same age and site conditions. (Pl. V.) 
When two trees of the same size, one healthy and the other heavily 
aistletoed, are compared—Trees No. 103 and No. 107, for instance— 
it is seen that it has taken the mistletoe-infected tree more than twice 
the number of years to reach the same size as the healthy tree. The 
average ratio of the leaf surface in square feet to the total volume in 
cubic feet for the healthy trees given in Table 16 is 409.7 compared 
with 185.5 for the heavily infected trees. 
Trees heavily infected with mistletoe not only have considerably 
shorter leaves and leaf tufts than healthy trees, but the leaves of 
mistletoe-infected trees are lighter in color than those of healthy 
trees, being a yellowish green as compared with the olive green on 
the healthy trees. Each heavy infection causes a localization and 
reduction of the photosynthetic or assimilatory leaf surface of the 
tree, which in turn results in a marked decrease in the rate of growth. 
EFFECT ON LONGEVITY OF HOST. 
A number of permanent sample plots were established on the Coco- 
nino and Tusayan National Forests by the Fort Valley Forest 
Experiment Station, in 1909, to determine the rate of growth and 
decadence, the rate of establishment of natural reproduction, and the 
effect of various factors upen regeneration on cut-over areas. These 
plots were remeasured in 1914 and 1919. Some of the plots yielded 
valuable data on the amount of mistletoe infection and the resulting 
mortality on cut-over areas. 
