First Report on the Flora of IVyontiJig. 59 



posure may produce a more truly Alpine flora than 9,000 

 feet with another. 



Many species hold their own at almost all altitudes, 

 and beginning with the lower altitudes, are successively 

 in blossom throughout the season at higher and higher 

 elevations. On the other hand, in given areas, a few 

 certain plants are never met with except within a given 

 range of elevation, but this given elevation differs for dif- 

 ferent parts of even the same state. It seems to be a 

 a relative point depending as much upon the elevation of 

 the surrounding country as upon the actual elevation 

 above sea-level. It follows, therefore, that plant zones 

 can only be established for a given area, as for instance, 

 the Laramie Plains and the mountains that rise on either 

 hand of it. 



It has been well pointed out by Dr. Coville in his 

 report on the "Botan}- of the Death Valley Expedition" 

 that only certain plants can be taken to mark zonal lines. 

 That only a few comply with the two characteristics of a 

 good zonal plant, \'iz: "It shall have a definite termina- 

 tion at the borders of a zone or at lines substantially par- 

 allel thereto, but closer together." "That the belt of a 

 zonal plant should be continuous." In any region I think 

 this may be found true of a very small number of plants, 

 but the large majority which have to be fitted into 

 these zones will so overlap from zone to zone that no 

 sharp distinctions can be drawn. Of course, between the 

 lowest and the highest zone of a given area the character- 

 istics are quite distinctive. These represent essentially 

 different floras with as little in common as the vegetation 

 of the plains and that of the adjacent mountains. 



In this report it has not seemed wise to try to estab- 



