DESCRIPTION OF PLATES. 
PuatE 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 sapwood. 
Puate I].—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. 
Prats II].—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 ponderose). 1. Leaves froma healthy tree. 2. Leaves froma ‘‘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. 
Puate 1V.—Fig. 1. Group of bull pines (Pinus ponderosa) near Elmore, 8S. 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. 
PiatTe 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. 
PuatE 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 isa ‘‘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. 
Prate VII.—Mycelium and fruiting bodies of the ‘‘blue”’ and ‘‘red-rot’”’ fungi. 1. 
Tangential section of ‘‘blue’’ wood; im, cross sections of hyphe of the blue fungus 
( Ceratostomella pilifera (Fr.) Winter), growing in the medullary rays; h, hyphe 
growing longitudinally in the wood fibers. These hyphe are brown. 2. Cross 
section of ‘‘blue’’ wood, showing longitudinal section of medullary ray with 
hyphe of the ‘‘ blue”’ fungus (fh) growing in the ray and into adjoining cells; the 
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