60 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



THE HUDSONIAN ZONE. 



This is the highest of the timbered phmt zones, its average altitude 

 in Washington being from 1,500 to 2,300 meters (5,000 to 7,500 feet). 

 The most widespread and characteristic tree in all the northwestern 

 mountains is the subalpine fir {Abies lasiocarpa) (PI. XVII). In 

 the Olympic and Cascade mountains this is always accompanied by 

 the black hemlock {Tsuga mertemiana), a tree which recurs locally 

 in the Bitterroots of Idaho, but which is unknown in the Blue Moun- 

 tains save on a single peak. It is not known whether this tree occurs 

 in the Okanogan Highlands. In the Olympic and Cascade moun- 

 tains the Alaska cedar {C hamaecij paris nootkatensis) is likewise a 

 characteristic tree, but it does not occur eastward from the latter 

 range. The white-bark pine {Pinus albicaulis) also belongs to this 

 zone, and reaches a higher altitude than any other Washington tree. 

 It is absent from the Olympics, but occurs nearly throughout the 

 Cascade Mountains, and appears again on the higher peaks of the 

 Blues and Bitterroots. 



Comparatively few shrubs and herbs are definitely limited to this 

 zone. Among the more conspicuous are an azalea {Rhododendron 

 albiflorum), a currant {Ribes howellii), and the western mountain 

 ash (Pyrus occidental is) . In places the bear grass (Xerophyllum 

 tenax) occupies acres of ground, but this plant occasionally occurs as 

 low as the Transition zone. 



In the following table is given a list of the characteristic Hud- 

 sonian species, showing their known appearance on the principal 

 peaks of the Cascade Mountains, namely. Mounts Stuart, Rainier, 

 Adams, St. Helens, Hood," Mazama,* and Shasta.*' Only small col- 

 lections have been made on Mount Baker, and ^or this reason the 

 species known to occur in the Cascade Mountains between the 48th 

 and 49th parallels are lumped for comparison. The table also shows 

 which species occur in the Arctic regions, in the Olympic Mountains, 

 in the Blue Mountains, in the Rocky Mountains as a whole, and in 

 the Sierra Nevada. 



a Howell, Thomas. The Flora of Mount Hood, Mazama, vol. 1, pp. 28-48, 1896. 



6 Coville, Frederick V. The August Vegetation of Mount Mazama, Mazama, 

 vol. 1, pp. 170-203, 1897. 



c Merriam, C. Hart. Results of a Biological Survey of Mount Shasta, North 

 American Fauna, no. 16, 1899. 



