ILLUSTRATIONS. 



Page. 

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



bull pine, showing blue color Frontispiece. 



]I. Dying trees of the bull pine. Fig. 1. Green, "sorrel-top," and 



' ' red-top ' ' trees. Fig. 2. Green and ' ' sorrel-top ' ' trees 40 



III. Color change in leaves of the bull pine. 1. Leaves from healthy 



tree. 2. Leaves from "sorrel-top" tree. 3 and 4. Leaves from 

 trees turning to the "red-top" stage 40 



IV. Fig. 1. "Red-top" tree in a group of healthy trees near Elmore, 



S.Dak. Fig. 2. "Black-top" trees 40 



V. Figs. 1 and 2. Sections of trunks of the bull pine, showing early 



stages of "blue disease " 40 



VI. "Blue" sections from dead trees. Fig. 1. Sections from tree dead 



five months. Fig. 2. Sections from tree dead eighteen months . . 40 

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

 1. Tangential section of "blue ' ' wood. 2. Cross section of ' ' blue' ' 

 wood. 3. Cross section of a medullary ray. 4. Young perithecium 

 of the ' ' blue ' ' fungus. 5. Mature perithecia of the " blue " fungus. 

 6. Two perithecia of the "blue" fungus. 7. Two asci with spores 

 of the "blue" fungus. 8. Spores of the "blue" fungus. 9. Top 

 of beak of perithecium of Ceratostomella pilifera just after the dis- 

 charge of the spore mass. 10 and 11. Median sections of sporo- 



phores of the ' ' red-rot ' ' fungus 40 



VIII. Sections of "blue" wood. Fig. 1. Radial section. Fig. 2. Tan- 

 gential section 



IX. Pieces of wood from the bull pine, showing blue fungus starting 



from holes made by a wood-boring beetle 40 



X. Sections showing early stages of the "red rot." Fig. 1. Section 

 taken 35 feet from the ground from a dead tree. Fig. 2. Section 

 showing more advanced stage of decay. Fig. 3. Section from tree 



shown in fig. 2, made 15 feet higher up 40 



XI. Sections from "black-top" bull pines, showing advanced stages of 

 decay. Figs. 1 and 2. Sections from the top of a fallen tree. Fig. 



3. Section from a standing pine 4 feet from the ground 40 



XII. Group of broken " black-top" trees 40 



XIII. Fig. 1. Top of "black top" broken off. Fig. 2,Polyporus pon- 



derosus growing on dead pine stump 40 



XIV. Sections of rejected cross-ties. Fig. 1. Wood affected with "red 



rot." Fig. 2. Diseased wood from living tree 40 



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