246 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Zone seems to include also some of the meadows above the timber, 

 but it is impossible to draw any sharp line here. Sometimes the 

 heavy timber of the Canadian Zone borders directly upon alpine 

 meadows, without any intervening transitional zone. 



The characteristic trees of the Hudsonian Zone are the alpine fir 

 and whitebark pine, but the fir, of course, grows also at lower 

 altitudes. Douglas fir and limber pine sometimes grow about 

 timber line, and the alpine larch grows here if anywhere in the 

 park. At the upper limit of timber the wind blows violently much 

 of the time, and for most of the year the ground is covered with 

 snow, so that trees find existence difficult; consequently, most of 

 them are stunted or twisted, and many are mere shrubs. Frequently 

 they are bent down by the wind and snow, their trunks lying flat 

 upon the ground. In such cases their branching is abnormally 

 dense, and these stunted trees often form impenetrable thickets. 



The principal shrubs of the zone are willows (Salix vestita), green 

 alder, spiny currant, pink meadowsweet, red raspberry, mountain- 

 agh, menziesia, Rocky Mountain laurel, red and white heather, 

 whortleberries (Vaccinium membranaceum and V. scoparium), and 

 elderberry. The laurel and heathers are practically confined to this 

 zone, but the other shrubs are more widely distributed. 



The herbaceous vegetation is rather varied, and because of abun- 

 dant moisture it is remarkably luxuriant. Here are found more 

 lavish displays of color than at any other level, and the meadows are 

 often an indescribable riot of color. The flower displays endure 

 longer here than elsewhere, for snow banks lie until the end of the sum- 

 mer, and as they melt new beds of flowers are coming continuously . 

 into bloom. The following list indicates the characteristic herbaceous 

 plants of the Hudsonian Zone: 



Phleuvi alpinum. Viola glabella. 



Xerophyllum tenax. Angelica dawsoni.* 



Tofieldia inUrmedia. Gaultheria huviifusa.* 



Streptopus amplexi/olius. Dodecatheon paucifiorum. 



Polygonum bistortoidcs. Gentiana calycosa.* 



Silene multicaulis. Romanzoffia sitchensis. 



Trollius albiflorus. Lappula diffusa. 



Aquilegia flavescens. Mimulus lewisii. 



Thalictrum megacarpum. Castilleja spp. 



Delphinium depauperatum.* Pedicularis groenlandica. 



Pulsatilla omdentalis.* Pedicularis bracteosa. 



Tiarella unifoliata. Valeriana sitchensis. 



Sibbaldia procumbens. Aster engelmannii. 



Hypericum scouleri. Erigeron salsuginosus.* 



Antennaria racemosa. Senecio rnegacephalus.* 



Arnica spp. Senecio ovinus. 

 Senecio triangularis. 



