(14 FORKST niSTKIHfTloN 



Iceland to (ireenland and Kamtchatka a mild temperate climate 

 prevailed and forests like these from New Knyland to Virginia 

 and California (l;.thed the land. In the words of (Jray (20): 

 "We appear to In- within the limits of scientific inference when 

 we announce that our existing temperate trees came from the 

 north." All species were proba'ily crowded southward by the 

 ice and doubtless found at least a narrow /one suited for their 

 occupation during the period of glaciation. Vpou the retire- 

 ment of the iee some of these species or their descendants must 

 have reoecupicd portions of the land. During all of this period 

 selective influences were undoubtedly sifting out the spe ies 

 which were the distant forebears of our present flora. Climatic, 

 topographic, and edaphic conditions determined the final types 

 of vegetation (prairie, forest, etc.) over larue areas of the land 

 reorcupied. Since none of the existing species of this region, 

 as far as we know, have appeared in the Tertiary deposits it 

 seems probable that they have entered or evolved since tint 

 period. 



The present alpine flora of the northern Rockies shows 

 little evidence of its connection with the Tertiary flora above 

 mentioned. Few species are common to the old and new world, 

 and no closely related forms are here known in the fossil stale. 

 Iiydbcru: (."MI mentions one woody plant, a dwarf willow (SaH.r 

 // In i/litfii) as common to the arctic regions of both continents 

 and to the higher altitudes of the Alps and the Rockies. 



Beyond a few other shrubby willows and heaths, with affin- 

 ities more or less evident with European species, immediate <-on- 

 ne.-tion between the woody alpine flora of this region and that 

 of the old world can hardly be admitted. As to some of the sub- 

 alpine species admitting the difference of opinion as to the 

 identity of the old and ne\v world forms of .1 n i'ii>< riis Sultltni 

 and COmtnUriis a few may be cited as having uvneral circiim- 

 polar distribution in the piv-._Harial period. Probably a consid- 

 erable IHIMI'HT of plants may be regarded as indiirenoiH to the 

 northern K'ocky .Mountain region since the ulaeial period. Cer- 

 tain sperj.-s considered by some to be transcontinental are by 

 tilers divided into t \\ o or mure species with lesser ran yes con- 

 is or overlapping: with ,iit con/idei-iuL: the merits of these 



