1917] VESTAL—FOOTHILLS VEGETATION 367 
there are no pines. The trees frequently do modify conditions of growth for 
ground plants, however, where pine needles accumulate, but this effect is very 
local. Farther up, and to the north, and apparently more closely associated 
with pine growths, the bearberry (see under Arctostaphylos association) is an 
sees part of the ground-cover between scattered trees 
niperus scopulorum is an infrequent though Scully conspicuous tree 
alas found with the pines. Pseudotsuga mucronata also mixes in to some 
extent, even in a few fairly xerophytic stations. Juniperus communis sibirica 
is a ground shrub of infrequent occurrence. Pinus flexilis is very locally 
represented, although not confined to the foothills. Pinus Murrayana, the 
se 4.—Shallow ravine head; mostly grassland, with fine soil at bottom, and 
thinn rae rockier soil on side-slopes; in coarse soil are numerous pines and Arcto- 
stephylis (foreground); in middle ground a considerable reat of Prunus demissa 
(leafless condition), occupying soil moist from seepage; April 1 
lodgepole pine, of the montane zone, mixes with the rock pine in the upper 
foothills. The rock pine is by no means absent from the montane zone, and is 
even quite abundant there if the lodgepole is absent, as in the Pike’s Peak 
highland generally. 
e ae association in its unmixed form (practically closed forest) has 
very few o spaces. Natural pruning of the lower branches is general. Old 
needles strew ibe ground; the light is much reduced; the two influences, mulc 
and shade, acting together or singly, exclude practically all ground plants from 
the closest stands, and all but a few from less dense forests. ants of primitive 
grassland very seldom persist in shac Relics of former vegetation are seen 
in less advanced stages, including acted plants of Opuntia, Cercocar pus, 
