1918] ROBBINS—BOULDER PARK 523 
SPHAGNUM BOGS.—Sphagnum moss is found in very small 
amounts here and there in the Park, but in no place is there any 
approach to the formation of sphagnum moor. Small sphagnum 
moors are occasionally found at higher elevations in heavily 
forested areas in northern Colorado, but never are they as well 
developed and characteristic as those found north and east in the 
United States. 
For the optimum development of sphagnum, there must be 
abundant precipitation, slow evaporation from the surface, slow 
percolation and run-off of soil water, low temperature, and absence 
of drying winds. In only favored situations are such conditions 
found in Colorado. Boulder Park is a very unfavorable locality 
for the development of sphagnum moors. Here the drainage is 
generally good, the temperatures of both air and soil may run high, © 
at least for a short period, many seasons are dry, and the winds are 
desiccating. In his description of the bog plant societies of northern 
North America, TRANSEAU (24) has selected 15 characteristic bog 
plants: Menyanthes trifoliata, Dulichium arundinaceum, Comarum 
palustre, Scheuchzeria palustris, Eriophorum polystachon, Drosera 
rotundifolia, Sarracenia purpurea, Oxycoccus oxycoccus, Chiogenes 
hispidula, Andromeda polifolia, Chamaedaphne calyculata, Ledum 
groenlandicum, Kalmia glauca, Betula pumila, and Larix laricina. 
Of these, Eriophorum polystachyon is the only one found in Boulder 
Park, and it is rare. Menyanthes trifoliata has been found in a bog 
a number of miles north of Boulder Park. 
The writer is indebted to Dr. H. C. Cow Es, under whom this 
study was conducted, for his helpful suggestions and criticisms; to 
Professor FRANCIS RAMALEY for valuable advice and for laboratory 
facilities granted at the Mountain Laboratory for Field Biology 
(Tolland, Colorado); to Professor AVEN NEtson, who identified 
a large number of the specimens; and to Mr. A. S. HrrcHcock for 
the identification of some difficult species of Poa. 
STATE AGRICULTURAL COLLEGE 
Fort Coxtris, Coto. 
