92 



8ILVA OF NORTH AMERICA. 



conifer-;e» 



and its power of reproduction under favorable conditions ^ make it the most valuable inhabitant of the 

 great coniferous forest of the northwest^ which it ennobles with its majestic port and splendid vigor. 



^ In the coast region from southern British Columbia nearly to 

 the northern borders of California seedling plants of Pseudotsuga 

 mucronata soon cover the ground from which the forest has been 

 cleared by fire, and, standing almost as close together as blades of 

 grass, grow on good soil with astonishing rapidity, forming tall 

 slender poles destitute of branches and foliage except at the very 

 top. An average upward growth of five or six feet is not unusual 

 on such trees, and leading shoots of Pseudotsuga mucronata ten feet 

 long may be seen near the shores of Puget Sound. These young trees 

 also increase their trunk diameter rapidly. A stem examined by 

 General Henry L. Abbot on the Solduc Hiver in northwestern Wash- 

 ington in 1896 had attained a diameter of six inches in ten years 

 and of twelve inches in twenty-three years, and had increased to 



eighteen inches by its forty-fourth year. In the same region a tree 

 only one hundred and forty-two years old had a trunk three feet 

 four inches in diameter at three feet above the surface of the 

 ground. This, however, is an exceptionally favorable region for 

 the rapid growth of trees on account of the rich soil and the exces- 

 sive rainfall. The log specimen in the Jesup Collection of North 

 American Woods in the American Museum of Natural History, 

 New York, procured in the neighborhood of Portland, Oregon, is 

 twenty-nine inches in diameter inside the bark and three hundred 

 and thirty-six years old, the sapwood, which is only an inch and 

 three eighths in thickness, showing sixty-six layers of annual growth. 

 In the dry interior part of the continent the Douglas Spruce in- 

 creases much more slowly and is by no means a fast-growing tree. 



EXPLANATION OF THE PLATE. 



Plate DCVII. Pseudotsuga muckonata. 



1. A flowering branch, natural size. 



2. A staminate flower, enlarged. 



3. An anther, front view, enlarged. 



4. An anther, side view, enlarged. 



5. A pistillate flower, enlarged. 



6. A scale of a pistillate flower, upper side, with its bract and ovules, 



enlarged. 



L 



7. A fruiting branch, natural size. 



8. A cone from Marvin Lakes, Colorado, natural size. 



9. A cone-scale, upper side, with its seeds and bract, natural size. 



10. Bracts from the base of a cone, natural size. 



11. A seed, enlarged. 



12. Vertical section of a seed, enlarged. 



13. An embryo, enlarged. 



14. Cross section of a leaf magnified fifteen diameters. 



15. Winter-buds, natural size. 



16. A seedling plant, natural size. 



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