250 FRANCIS RAMALEY 



Divide at the west^ filling the valley with ice and no doubt 

 modifying its topography. Within the park now there are 

 morainic knolls and hollows except where the stream has worked 

 over the deposit leaving low terraces, or where the drying of 

 ancient lakes has exposed their flat beds to be clothed with 

 vegetation. Since none of the hills surrounding the park were 

 glaciated to the top it is to be supposed that their flora was not 

 destroyed during the period of glaciation although probably 

 the climate was cold enough to kill out the more southern types. 

 This is indicated by the present composition of the flora which 

 shows largely northern affinities. When the glaciers finally 

 disappeared there was still at hand a supply of plants to occupy 

 the land exposed. 



It will not be necessary here to decide why mountain parks 

 are largely grass-covered rather than forested. The old problem 

 of the prairies is here for solution. That it is by no means a 

 simple problem may be gathered from suggestions that have 

 been offered.'' 



Of the present park grassland some along stream courses or 

 near ponds is mesophytic, being characterized by meadow 

 grasses and sedges and a profusion of flowering herbs forming a 

 close stand with verj^ little bare ground. This may be desig- 

 nated as "meadow." The xerophytic part, which is always 

 rather open, and made up almost entirely of low-growing plants, 

 is in this paper called ''dry grassland." 



As our discussion proceeds it will be noted that practically 



^ Ramaley, Francis, 1910, I.e. 



Henderson, JuniuS; Extinct glaciers of Colorado. Univ. Colo. Studies 3: 

 39-44, 1905. 



^Shimek, B., The prairies. Bull. Lab. Nat. Hist. Univ. of Iowa 6: 169-240. 

 1911. 



Gleason, H. A., The vegetation of the inland sand deposits of Illinois. Bull. 

 III. State Lab. 9: 23-174, 1910. 



Gleason, H. A., Some unsolved problems of the prairies. Bull. Torr. Bot. 

 Club, 36.- 265-271, 1909. 



Pound, Roscoe and Clements, Frederic E., The vegetation regions of the 

 prairie province. Bot. Gaz. 381-94, 1898. 



Harshberger, John W., Phytogeographic Survey of North America (Engler's 

 "Die Vegetation der Erde"). Leipsic, 1911. 



