International Excursion in America. 
35 
of the route the “sweet clover” (Melilotus alba) is exceedingly 
abundant and luxuriant as a roadside weed, far more so than in 
Europe, often forming pure stands for some distance along the 
wayside: indeed the abundance and luxuriance of this plant right 
through the continent from east to west, except in the driest and 
most alkaline regions, is a very striking phenomenon to a European. 
It seems that in temperate North America the plant has found 
much more favourable conditions than exist in Europe, its native 
home. Typha latifolia and Scirpus validus (?~lacustris ) occur here 
and there in wet places, along the sides of the railroad tracks and 
elsewhere right through the prairie and plains regions, growing in 
places where no open water exists, rather a striking difference from 
their ordinary European habitats. 
The Rocky Mountain Foothills. 
August 12th was spent in an excursion from Palmer Lake into 
the “ Black Forest,” a great area of Pinus scopulonim (the Rocky 
Mountain form of the far western Yellow Pine, P. ponderosa), 
stretching out from the mountains on higher ground into the Great 
Plains, and with an average elevation of 1,000 feet above the latter. 
It occupies the watershed between the Platte river on the north and 
the Arkansas river on the south. The undergrowth of the pine 
forest consists largely of Antostuphylos Uva-nrsi, with MuJdenbergia 
gracilis, Carex scoparia, etc. The highest ridge of the forest has 
Douglas fir, representing the next higher stage in the Rocky 
Mountain zonation, but this ridge was not visited. 
The pine forest is fringed with “ chaparral ” or, as we should 
call it, scrub, 1 dominated by the three species Cercocarpus parvifolius, 
Quercus Gunnisonii (a scrub oak), and Rhus trilobata, which are 
often mixed, but sometimes zoned. According to Professor Clements 
they have different water demands in an ascending series, and 
correspondingly the last-named species extends furthest eastwards. 
The chaparral often forms fairly dense thickets and casts a deep 
shade. It shelters various shade forms of species which also grow 
in the grassland outside, such as Achillea lauulosa (close to A. 
millefolium), Helianthus rigid us, H. pumilus, Agrostis hiemalis, as 
well as shade species—such as Fragaria vesca —which also occur 
in the Rocky Mountain forest. 
The grassland which generally occupies the floors of the natural 
amphitheatres—the slopes of which are fringed with chaparral* 
the higher ground being covered with pine forest—is part of the 
1 To be distinguished from the “ true ” Californian chaparral which is 
sclerophyll scrub quite analogous to Mediterranean maqiiis 
