42 



knowledge of the range of variation shown by S, phylicifolia Sir 

 Joseph D. Hooker defers in his Student's Flora of the British 

 Islands) writes me; ''I have carefully examined the White 

 Mountain willow, and felt quite satisfied in my own mind that it 

 cannot be distinguished specifically from our European //y/Z/ayb- 

 lia!' This is temperate, but none the less decisive. I would, 

 however, go further and say that often the resemblance is so 

 close as to include even those slight peculiarities of '* size, form 

 and color," which we expect to find in two plants of the same 

 species when growing side by side. 



Will the reader bear with a bit of personal experience which 

 brought this conviction home to my mind. Last winter I was 

 comparing two sheets of loose specimens, spread out on the table 

 before me ; one set from the White Mountains, collected by Mn 

 Faxon ; the other from Lapland, collected by Dr. Hakansson. 

 Both were fresh, admirably prepared, and as it happened both 

 had been taken in exactly the same stage of development I had 

 carelessly picked up a twig of fruiting aments to examine 

 with the hand-magnifier, but when I came to return the speci- 

 men I had forgotten (or to be more exact, I had failed to notice 

 in the first place) from which sheet it had been removed. Super- 

 ficial resemblances or differences to guide me in replacing the 

 specimen in hand there were none. I soaked up capsules of the 

 two plants, American and European, placed them Under the 

 microscope and carefully compared every minute character of 

 scale, pedicel, style, stigmas, etc. Mind, I was not looking for 

 specific distinctions, I only wished to find some slight individual 

 peculiarity which would enable me to replace my specimen. I 

 felt piqued to think I should be so baffled, but finally, sooner 

 than vitiate the Integrity of the remaining material, I threw my 

 twig of questionable belonging into the fire ! I do not wish to 

 be understood as making the sweeping assertion that all the 

 White Mountain and Labrador phylicifolia is equally undistin- 

 guishable from the European, for I know very well that some 

 forms can be, at once, recognized as peculiarly American. What 

 I do claim is that from a meeting-ground of perfect similarity the 

 American forms diverge not more widely than do the European 

 of the same species. 



