356 University of California Publications in Zoology. \Vou.9 
Valeriana sitchensis Bong. Valerian. 
The herbaceous vegetation above timber-line is composed in 
part of this species. Collected on Montague Island. (No. 28.) 
Arnica chamissonis Less. 
Collected at the head of Port Nell Juan. (No. 49.) 
Senecio pseudoarnica Less. Beach Senecio. 
This large, heavy-leafed composite is a characteristic growth 
of the marine littoral. On the beaches it is associated with 
Elymus, Lathyrus, Aquilegia, Arenaria, and Rubus spectabilis. 
(No. 57.) 
DISCUSSION OF DISTRIBUTION. 
Two divisions of the Boreal Region are represented in the 
Prince William Sound district, the Hudsonian Zone and the 
Aretic-Alpine Zone.* 
All the area covered by coniferous forests is comprised in the 
IHudsonian Zone, that is, all the country below timber-line. In 
the Sound region there is little uniformity in the altitude to 
which forests extend. This is chiefly due to the effects of slope 
exposure and the direction of the prevailing winds. On south- 
ern exposures and on low islands, free from the chilling effects 
of large masses of perpetual snow, timber-line may extend to an 
elevation of 2000 feet or more. On north exposures this line 
often drops to 500 or 1000 feet, and at the heads of some of the 
inlets as low as sea-level. 
The two conifers which are uniformly present at timber-line 
are Tsuga mertensiana and Picea sitchensis. With these a few 
individuals of Tsuga heterophylla struggle to the limit of tree 
erowth in some localities. With this forest occur either seat- 
tered through it or as a fringing growth on its margins the 
following shrubs: Alnus sitchensis, Ribes bracteosum, Aruncus 
sylvester, Rubus spectabilis, Pyrus sitchensis, Pyrus diversifolia, 
Echinopanax horridum, Menziesia ferruginea, Cladothamnus 
pyrolacflorus, Vaccinium ovalifolium, Sambucus racemosa, and 
Viburnum pauciflorum. 
2 For deseription of similar conditions, as prevailing in the Cook Inlet 
region of Alaska, see Osgood, North American Fauna No. 21, 1901, p. 59. 
