4 LETTER FROM M. E. BOURGEAU. 



at Carlton: the species are not numerous, for which reason I 

 have collected both male and female specimens of each plant, and 

 have been careful to put corresponding numbers on each sex. 

 There are a good many duplicates ; therefore I trust you may 

 have as many specimens as will enable you to study them satis- 

 factorily. I regret not being able to send you the leaves of the 

 Salices ; they are not yet developed. During the third week of 

 last month, the catkins of P. halsamifera have been frozen and 

 have fallen oiF; several other plants, also in flower, have been 

 frozen, and thus for a week I have been deprived of my ex- 

 cursions. 



Observations referred to in the foregoing Letter, on the Tempera- 

 ture of the Earth and of Forest-trees, made at Fort Carlton, 

 on the Saskatchewan. 



