ECOLOGICAL NOTES 113 
hills a few kilometers to the west. These plains have a dry grassland 
vegetation with Cercocarpus on any sharp knoll-tops and with soap- 
weed (Yucca glauca) on the south exposures of rounded eminences. 
Low grasses and low species of Artemisia form probably four-fifths of the 
soil cover. Other plants which are somewhat abundant are Aragallus 
multiflorus, Aragallus lamberti, Leucocrinum montanum, Tetraneuris 
acaulis, Oreocarya virgata, Arenaria hookeri, Euphorbia robusta, O puntia 
missouriensis, Cactus missouriensis, Harbouria trachy pleura, Homalobus 
caespitosus, Senecio douglassu, Eriogonum alatum, Chrysothamnus 
platiensis, Astragalus drummondii, Pulsatilla hirsutissima. In shallow 
draws Symphoricar pos occidentalis, Rhus irilobata and Prunus melano- 
carpa occur. The soil of these plains is very coarse, derived from the 
conglomerates of the sedimentary series, but it is so slightly disintegrated 
that it is often difficult to distinguish it from decomposed granite. This 
area is interesting from the fact that the plants other than grasses and 
species of Artemisia are so abundant both in species and in individuals. 
It differs in this respect from the usual valleys of the sedimentary region. 
Probably this is because here it is conglomerate which has made the soil, 
while in other valleys it is a fine-grained sandstone and much better. 
calculated to support grass and sagebrush but not so suitable for other 
plants. 
A Square Mile of Rock Ridge and Foothills.—A study was made 
of a square mile (Section 35; T. 12, N.; R. 70, W.), and a vegeta- 
tion map made, which is here reproduced. On this map are shown the 
various formations. The relative frequency of the various kinds of 
plants is also indicated, where a close formation occurs the conventional 
signs used are put close together. The signs used do not, however, 
represent individual plants. The plant formations’ of this square mile are 
those found generally in the northern part of Larimer County, Colorado, 
along the contact of the granites and the sedimentary deposits, viz.: 
Cercocarpus Scrub Formation, Valley Grassland, Upland Dry Grass 
Formation, Canyon Forest Formation, Foothill Forest Formation. 
Plants of a U-shaped Gulch.—The gulch studied is about 4oo feet 
wide as measured.along the ground surface. North Box Elder Creek, 
* These formations are somewhat fully discussed in the article previously cited. 
