33^ 



BOTANICAL GAZETTE 



[may 



the forest formation is advancing in the canons, but that on the ridges 

 it has reached its cHmatic limit. The aged, battered, and twisted 

 white pines, with no young trees among them, indicate a repulse in 

 the effort of the forest to ascend the ridges; while, on the other hand, 

 the gradual decrease in height, the scattering of individuals and 

 groups in advance of the main mass, suggest that in the canons the 

 forest is still advancing — that it has not yet reached the point where 

 tree growth is climatically excluded. Harvey^ has cited a similar 

 condition in evidence that the forest is not climaticallv excluded 

 from the summit of Mt. Ktaadn. It is an interesting fact in this 

 connection that the Picea Krummhoh in the canons of the Long's 

 Peak region bears a striking resemblance, in type of trees represented, 

 in the Krummhoh form which they take, and in the manner of their 

 seeming advance, to the mesophytic Picea-Abies Krummhoh of the 

 eastern mountain. 



It will be wtII at this point to recall the fact that the agency most 

 important in preventing tree growth is dry w^ind during frosty weather, 

 since it accelerates transpiration to a high degree, while the frozen 

 condition of the ground prevents a renew^al of the water supply.^ The 



-the permanent timberline on 

 the exposed ridges and the advancing forest in the sheltered canons 

 agree perfectly with this theory. 



conditions in the Lono;'s Peak region 



EXPOSED SLOPES 



Dry Meadow 



Succession 



CANONS 



Wet Meadow-Forest Succession 



Lichens 



Xerophytic Herbs 



Basins and Watercourses 



Mosses 



Sedf^res and Grasses 



Dry Meadow Plants 



Joints 

 Crevice Plants 



Mature Dry Meadow 



Climatic Timberline 

 Pinus flexilis Forest 



Mature Wet Meadow 



I 



Shrubs 



Picea Krummholz 

 Picea-Abies Forest 



^ Har\t:y, LeRoy H., Op. ciL 



5 Kiklman; referred to by Schimper, Plant geography 78 



