No. 603] 



THE BOLE OF ISOLATION 



179 



not fail to be impressed by the prevailing humidity of 

 both soil and atmosphere in this region. In the dense 

 shade of the great redwoods the ground is damp, even 

 during the summer months, and the fallen logs are cov- 

 ered with mosses and fungi. 



When we cross Humboldt Bay to the narrow peninsulas 

 separating this body of water from the ocean (Fig. 1), 

 we enter a quite different environment. No redwoods are 

 found, the woods, where present, are open, and the ground 

 is prevailingly dry and sandy. In the wooded area, ex- 

 tending down the axis of the northern peninsula, the pre- 

 dominant tree is a small pine {Pinus contorta), though 

 the waxberry and willow (Salix hookeriana) are likewise 

 abundant, and small specimens of the Sitka spruce are 

 fairly common. Among the more frequent shrubs are 

 the huckleberry {V. ovatum), the twinberry (Lonicera 

 involucrata) and silk tassel bush {Garry a elliptica). The 

 ground is largely covered by two plants of trailing habit, 

 the bearberry {Arctostaphylos uva-ursi) and the beach 

 strawberry {Fragaria chilensis). 



On its ocean side, the peninsula is bordered by a wide 

 strip of shifting sand. Here the process of dune forma- 

 tion may be witnessed to perfection, the dunes often 

 reaching a height of forty or fifty feet. In places the en- 

 croachments of the sand upon the hard-pressed vegeta- 

 tion are evidently rapid, solid ramparts of willows and 

 spruces being steadily engulfed by an advancing wall, 

 frequently as high as the trees themselves. Nevertheless, 

 even on the open sands of the dunes, certain trailing plants 

 maintain a precarious foothold. Among the commonest 

 of these are to be mentioned the yellow sand verbena 

 (Ahronia latifolia), the beach strawberry (F. chilnisis), 

 beach pea {Lathyrus littoralis), and two species of Fran- 

 seria {F. chamissonis and F. hipinjiafifida), wliile the suc- 

 culent Mesemhryanthemum npqnilnfernle is occasionally 

 met with. 



Despite the nearness to the ocean and the high atmos- 

 pheric humidity, the peninsula region seems dn' in com- 

 parison with the redwood forests. This is due in part to 



