[Vol. 2 



62 



ANNALS OF THE MISSOURI BOTANICAL GARDEN 



trees yield nothing worth mentioning; and where it is less 

 than 11° C, the cultivation of grain is uncertain. The mini- 

 mum limits of the necessary mean summer heat for the fol- 

 lowing wild Norwegian trees and shrubs appears to be as 



Fig. 2. Isotherm* for July. 



follows: for Fagus sylvatica, 13.4°C. ; Quercus pedunculated, 

 12.6°C. ; Corylus Avellana, Acer platanoides, and Tilia cor- 

 data, 12.5°C. ; Alnus glutinosa and Fraxinus excelsior, 12.4° 

 C. ; Sorbus Aria and Ulmus montana, 11.2°C. ; Picca excelsa 

 and Pinus sylvestris, 8.4°C. ; Alnus incana, Prunus Padus, 



