DESCRIPTION OF P1.ATES. 



PLATE I. Frontispiece. Cross section of the trunk of a dying tree of the western 

 yellow or bull pine (Pinus ponderosa) from the Black Hills, South Dakota. This 

 tree was attacked by the beetles in August, 1901. The section was cut at a point 

 6 feet from the ground during the early part of November, 1901. Note the beetle 

 holes in the bark; also the yellow ring between heartwood and sap wood. 



PLATE II. Dying trees of the bull pine. Fig. 1 shows several trees; at the left two 

 live, green trees, a "sorrel-top" tree in the center, and a "red-top" tree at the 

 right. Photographed August 5, 1902. Fig. 2 shows several live, green trees at 

 the left and a "sorrel-top" tree toward the right. Note that this tree is still 

 green at the top. Photographed August 5, 1902. 



PLATE III. Various stages showing the gradual color change of leaves of the bull 

 pine (Pinus ponderosa) after they have been attacked by the bark beetles (Den- 

 droctonus ponderosx ) . 1 . Leaves from a healthy tree. 2. Leaves from a 4 ' sorrel- 

 top" tree. 3 and 4. Leaves from trees changing to the "red-top" stage. When 

 the leaves have reached the stage of 4 they fall off and are completely dead. 



PLATE IV. Fig. 1. Group of bull pines (Pinus ponderosa) near Elrnore, S. Dak., 

 showing a " red-top " tree in the center and healthy trees on both sides. Fig. 2 

 shows a group of "black-top" trees from which all leaves have fallen. This 

 photograph was made in November, 1901, and it is probable that these trees 

 were attacked by the beetles in August, 1899. 



PLATE V. Sections of trunks of the bull pine (Pinus ponderosa), showing the 

 "blue" disease. Fig. 1 shows an early stage. This section was cut in Novem- 

 ber, 45 feet up in the trunk, from a tree attacked by the beetles in August of 

 the same year. The tree is still alive at this point. The blue color has started 

 at two separate points. Fig. 2. A later stage, showing the blue color spread out 

 over one-half of the section. Note the yellow ring at the border of heartwood 

 and sapwood. 



PLATE VI. Fig. 1. Three sections from a bull pine made in November, 1901. This tree 

 was probably attacked by the beetles the latter part of July, 1901. The sections 

 were made at points 5 feet, 16 feet, and 36 feet, respectively, from the ground, 

 i. e., the largest section was cut from the butt, the second one about half way up, 

 and the third in the top. The healthy wood photographs white, and all darker 

 shades represent blued wood. Note the beetle holes in the bark. Fig. 2. 

 Three sections from a bull pine made in November, 1901. This tree was prob- 

 ably attacked by the beetles in July, 1900. It is a " black-top" tree. The sec- 

 tions were made at points 4 feet, 26 feet, and 40 feet from the ground. All are 

 blue. The section near the ground shows " red rot." This happens frequently 

 where the bases of the trees are shaded by long grasses and bushes. In most 

 trees the base will be found sound. The whole tree was dead. 



PLATE VII. Mycelium and fruiting bodies of the "blue" and "red-rot" fungi. 1. 

 Tangential section of "blue" wood; m, cross sections of hyphae of the blue fungus 

 ( Ceratostomella. pilifera (Fr.) Winter), growing in the medullary rays; h, hyphse 

 growing longitudinally in the wood fibers. These hyphse are brown. 2. Cross 

 section of "blue" wood, showing longitudinal section of medullary ray with 

 hyphse of the " blue" fungus (h) growing in the ray and into adjoining cells; the 

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