192 BOTANICAL GAZETTE [September 



Amelanchier alnifolia, Primus pennsylvanica, P. americana, P. 

 demissa, Crataegus coloradcnsis et spp., Robiiria neomcxicana (in 

 the south only), Acer glabrum, and A. Neguudo, with a few others. 

 A few shrubs are present and a variable undergrowth, with one 

 typical aspect of Viola canadensis Rybd., Hydro phyllum, and 

 Galium. A Ligusticum is very abundant in places. 



Aspen association. — Populus tremuloides is restricted, in all but 

 the highest parts of the foothills, to relatively mesophytic ravines. 

 It does not come up abundantly following burning of the pine 

 forest, as is true in the higher elevations and farther north. 



Eastern Illinois State Normal School 

 Charleston, III. 



LITERATURE CITED 

 i. Dams, W. M., The Colorado Front Range. Ann. Ass. Amer. Geog. 



1:21-83. IQII. 



2. Fenneman, N. M., Geology of the Boulder district, Colorado. U.S. 

 Geol. Surv. Bull. 265. pp. 101. 1905. 



3. Gates, F. C, The relation between evaporation and plant succession in a 

 given area. Amer. Jour. Bot. 4:161-178. 1917. 



4. Gleason, H. A., and Gates, F. C, A comparison of rates of evaporation 

 in certain associations in central Illinois. Bot. Gaz. 53:478-491. 1912. 



5. Johnson, W. D., The High Plains and their utilization. Ann. Repts. 

 U.S. Geol. Surv. 21, part 4, pp. 599-741; 22, part 4, pp. 631-669. 1900, 

 1 901. 



6. Lee, W. T., The origin of the debris-covered mesas of Boulder, Colorado. 

 Jour. Geol. 8:504-511. 1900. 



7. Marvine, A. R. [The sedimentary rocks east of the Front Range (chap, 

 ii, pp. 93-137, in Marvine's report)], in Hayden, F. V., Ann. Rept. U.S. 

 Geol. and Geog. Surv. Terr, for 1873, embracing Colorado. 718 pp. 

 Washington, 1874. 



8. Ramaley, F., Plant zones in the Rocky Mountains of Colorado. Science 

 26:642-643. 1907. 



9. , Botany of northeastern Larimer County, Colorado. Univ. Colo. 



Studies 5:119-131. 1908. 



10. , Dry grassland of a high mountain park in northern Colorado. 



Plant World 19:249-270. 1916. 



11. , Vascular plants of the Tolland region in Colorado. Univ. Colo. 



Studies 12:27-51. 1917. 



12. Ramaley, F., Robbins, W. W., and Dodds, G. S., Studies in mesa and foot- 

 hill vegetation, I. Univ. Colo. Studies 6:11-49. 1908. 



