196 BOTANICAL GAZETTE [SEPTEMBER 
and farther east Picradeniospsis oppositijolia, sometimes accom- 
panied by Malvasirum coccineum, : 
A number of graded roads have been built very recently and 
these show only the very first vegetation, a ruderal annual vegeta- 
tion. The boulevard, which runs from Colorado Springs to 
Manitou, is an older road of this type, having been built for about 
thirteen or fourteen years. The first permanent succession on this 
road within the Bouteloua formation was Stipa Vaseyi, which is 
now giving way to Muhlenbergia gracillima and Bouteloua oligo- 
stachya, Many other species came in, among which the more 
important are Sitanion elymoides, Aristida longiseta, Schedonnardus 
paniculatus, Helianthus annuus, Quincula lobata, Astragalus bisul- 
catus, Sophora sericea, Grindelia squarrosa, with other plants from 
the formation, as well as ruderal species. 
One of the transects of this road deserves special mention. There 
is a cut here of about 2™, and the road runs north and south. The 
differences in the east and west sides are due entirely to the differences 
in exposure, and to its effect upon temperature and water content. 
The west side, which receives the most light, has first a distinct zone 
of Petalostemon oligophyllus, back of which there is a mixed zone of 
Boebera papposa and Xanthium commune; this is followed on the 
bank by Stipa Vaseyi, and this in turn by a crest zone largely of 
annuals. The east side shows first a zone of Xanthium commune 
followed by Stipa Vaseyi, mixed with Schedonnardus paniculatus, 
Boebera papposa, Psoralea tenuiflora, etc.; and this is followed on 
the steep unstable soil by annuals. Back of the annuals is the 
Bouteloua formation in which Muhlenbergia gracillima predom- 
inates. 
There is a great deal of variation in the species which first appear: 
Almost any one of the species cited under the ruderal formation 
may dominate in certain places, but the more or less typical examples 
mentioned above should serve to give an idea of the succession on 
roads. 
Reservoirs are generally built where only one side needs to be 
dammed. The outer slope of the dam is invaded in the same Way . 
road would be. An interesting exception is found at Palmers 
reservoirs. The large reservoir, which was built in 1902, had by 
