36 A. G. Tansley. 
Great Plains grassland formation, but is not here dominated by 
short-grass, and consists largely of Festuca ovina (forma ingrata) 
Bouteloua hirsuta , and Kceleria cristata, with Achillea lanulosa, 
Petalostenuim sp. Artemisia canadensis and Arenaria Fendleri , 
abundant. This grassland also covers the strikingly flat tops of 
the foothill “mesas”—the dissected remains of an old alluvial 
plain —and here is often dominated by the grama-grass, Ponteloua 
oligostachya, with Muhlenbergia punctata and Agropyrum Smithii 
forming nearly pure local patches (societies in the English use) 
and much Opnntia and Mamillaria vivipara, giving quite a typical 
Great Plains vegetation. 
On the evening of August 12th the party travelled—again 
southward—to the flourishing city and health resort of Colorado 
Springs, where the night was spent. On August 13th the party 
drove west to Colorado City, spending the day among the foothills, 
and examined the vegetation of Bear Canyon, of the Niobrara 
Limestone, which here forms a prominent foothill ridge, and of the 
“ Garden of the Gods ” with its towering masses of red Triassic or 
Permian sandstone. In this region the foothill thicket (chaparral) 
alternates with grassland and on the rocky slopes the most northern 
limit of the Pignon-Juniper formation is encountered. This last 
formation, dominated by Pinus edulis and Juniperus monospenna 
(Sabina scopulorum), has an immense extension to the southward 
through New Mexico and Arizona into Mexico. At this northward 
limit its specific flora is relatively poor, being mainly characterised 
by Stipa Scribneri with the fern Cheilanthes Feei on the rocks. It 
takes the rocky slopes with shallow soil, while the chaparral prefers 
the gentler slopes with a deeper soil. Examples of river bottom 
woods dominated by Populus Sargenti (the western form of the 
cottonwood) and with P. angustifolia, Acer Negnndo, etc. associated, 
sheltering quite a characteristic river-bottom vegetation, were seen 
in Bear Creek Canyon. In the evening the party walked from 
Manitou (6,500 feet) at the foot of the mountains up Engelmann 
Canyon which carries the Pike’s Peak cog-railway, to Minnehaha- 
on-Ruxton (8,330 feet) a beautiful spot in the Douglas fir-wood 
which covers the lower slopes of the Rocky Mountains, and here 
they were accommodated in Professor Clements’s two bungalows 
and in the inn. 
Rocky Mountains—Pike’s Peak Region. 
The next week was spent at Minnehaha as headquarters, and 
almost daily excursions were made to places in the neighbourhood, 
