436 BULLETIN OF THE BUSSEY INSTITUTION. 
I am led to the above conclusions by the fact that some years 
ago, for the purpose of keeping some willow cuttings over winter, 
I buried them in a bare sand bank from which all the original soil 
had been removed. By accident, a few of the cuttings were left 
in the sand where they sprouted and grew rapidly. After the 
second year, they grew from five to seven feet each year for more 
than twenty years without the application of any fertilizer, and 
without cultivation. During the past ten years, these willows 
have been permitted to grow without being cut; on examination I 
find that the sand beneath them is covered with a good soil. 
On submitting some of the fibrous willow roots to my colleague, 
Mr. E. W. Morse, for microscopic examination, he finds that while 
there are root-hairs upon some of the roots others are devoid of 
hairs and that the hairless roots are enveloped by fungus threads. 
It is to be inferred, therefore, from what is known of the power 
of fungi on the roots of forest trees to take nitrogen from the air, 
~ that a part at least of the nitrogenous food of my willows has 
been derived from the air—a conclusion which is consistent with 
the rapidity of their growth upon land which was naturally by no 
means fertile. 
