BOTANY OF LARIMER COUNTY I25 
This condition, while not universal, is to be considered as the rule. The 
grass, however, does not stop so abruptly, bunches of it extend all 
along up through the scrub. Although the shrubs occur only on the 
tops of the ridges and on the steep slopes, it must not be supposed that 
their distribution is determined by altitude and its consequent tempera- 
ture. This is easily proven because the ridges near Bellevue bear the 
shrubs in great number at an altitude of less than 6,000 ft., which is a 
thousand feet below the lower shrub line on the ridges east of North 
Box Elder Falls. Again it is to be noted that patches of grassland 
occur on level or gently sloping parts of the rock ridges wherever there 
is an accumulation of soil. Hence it may be said that soil is the con- 
trolling factor in determining the limits of scrub and grassland. 
The Cercocarpus bushes are about three feet tal] and are, as a rule, 
so closely placed that it is difficult to climb through between them. At 
any rate one must take a very zigzag course in going among them. 
Wherever there is an accumulation of soil they are farther apart with 
bunch grass and mountain sage between them. On ledges of rock 
containing lime salts the shrubs are often distantly placed giving a 
truly desert appearance. Pines and cedars when present do not inter- 
fere much with the shrubs as these seem able to grow up well under them, 
being tolerant of some shade. (Views of this formation are shown in 
Figs. 1, 2, 3, 4, and 5.) 
Collections were made from the rock ridges and from the list thus 
obtained together with field notes a selected list is formulated as giving 
the more conspicuous or common plants in the spring and early summer. 
Autumn plants are not known to the writer as the district was visited 
early in the season. However, some of the perennial plants which come 
into bloom later could be recognized from vegetative characters. No 
shrubs occur except Cercocarpus. Pine and cedar are the only 
trees. 
ParRTIAL LisT OF THE PLANTS OF CERCOCARPUS FORMATION 
Dominant SPECIES 
Cercocarpus parvifolius 
ConsPicuous SPECIES 
Pinus scopulorum Sabina scopulorum 
