. Bulletin of the Department of Agriculture. Agriculture; Agriculture. MISTLETOE INJURY TO CONIFERS. 23 infected, however, may continue to produce aerial branches of the mistletoe to a very advanced age. True mistletoe burls are probably of less frequent occurrence on Douglas fir than on any other economic tree species. Burls do occur, however, with sufficient frequency to be characteristic of mistletoe infection on the trunk of this tree. Large elongated mistletoe burls, including the entire circumference of the trunk, occasionally occur in heavil}^ infected trees in many parts of Idaho
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. MISTLETOE INJURY TO CONIFERS. 23 infected, however, may continue to produce aerial branches of the mistletoe to a very advanced age. True mistletoe burls are probably of less frequent occurrence on Douglas fir than on any other economic tree species. Burls do occur, however, with sufficient frequency to be characteristic of mistletoe infection on the trunk of this tree. Large elongated mistletoe burls, including the entire circumference of the trunk, occasionally occur in heavil}^ infected trees in many parts of Idaho and Montana (fig. 21). More frequently there is a series. Fig. 21.—Large mistletoe burl on Douglas fir caused by Razoumofskya douglasii. This burl is approximately 10 feet long and 2 feet in diameter at its widest part. Fig. 22.—A Douglas fir, showing numer- ous burls caused by Razouniofskt/a douglasii. The branches are heavily broomed. A high degree of infection, but a common condition, is shown. of individual burls, more or less confluent, on one trunk (fig. 22), each burl representing the seat of an old infection, from which the aerial parts of the parasite have long since disappeared. Longitu- dinal and cross sections through these burls show the characteristic fan-shaped areas of infection (fig. 23). In numerous cases the burls originate from infections at the base of branches. If the branch dies or is broken off, an open wound is formed in the center of the burl. Very peculiar swellings or small burls frequently occur on. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Dept. of Agriculture. [Washington, D. C. ?] : The Dept. : Supt. of Docs. , G. P. O.
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