50 RAMALEY: XEROPHYTIC GRASSLANDS AT 
of the plants recorded as belonging to the dry grassland would 
also be included in a list of mesophytes. One-third of the species 
are grasses. 
The systematic list includes a total of 256 species in 131 
genera and 35 families. The families best represented with the 
number of genera and species in each are shown below: 
Poaceae! iso eer. ae 25 66 UB ALB A ceca sok cS te 
 & COAG oe a3 SA's, ics Pabacese 552. hse 9 16 
Polygonaceae.......... ye : Aminiaceae.... 2.00.65. eee 
fUsinaceae. 0. fo ss eee es Boraginaceae.......... =, ae | 
Brassicaceae........... 6: 10 Carduacene «2225 iS: 23 55 
Only 5 species range the whole distance from mountain front 
to subalpine zone. Of the 50 species at Bryan Mountain 29 
extend down to Tolland and only 5 to the mountain front at 
Boulder. Of the 160 species at Boulder 40 range up to Tolland 
and 5 continue to Bryan Mountain. Floristically, then, the dry 
grasslands at Boulder and at Bryan Mountain are almost totally 
different, while a very considerable similarity exists between those 
of Boulder and Tolland and of Tolland and Bryan Mountain. 
SUMMARY 
The foregoing paper is based upon a study of grasslands in 
northern Colorado from the plains to the subalpine zone. A list 
is presented of all recognized xerophytic grassland communities 
in northern Colorado. From this list the author selects for com- 
parison those of the ‘mixed dry grassland type.” Environmental 
influences, the soil, temperature and rainfall are considered; the 
very low air and soil temperatures of the subalpine region being 
noted. To show floristic changes with altitude a systematic list 
of dry grassland plants is printed and the altitudinal distribution 
of each species indicated. At the mountain front there are 160 
species in the dry grassland, while the numbers at other stations 
are as follows: lower foothills 139, upper foothills 130, montane 
area 107, subalpine area 50. Of the last named nearly one-half 
are strictly high-altitude forms which do not extend down even 
to the montane zone. It is pointed out that a number of species 
belonging to moister situations ‘in the lowlands are able to enter 
dry grasslands of higher altitudes because of lower temperature 
