AMERICAN 
JOURNAL OF BOTANY 
Vol. I February, 1914 No. 2 
ON THE MYCORHIZAS OF FOREST TREES* 
W. B. MCDOUGALL 
I. INTRODUCTION 
The study of mycorhizas has engaged the attiention of numerous 
investigators since the appearance of Frank's (4) first paper on the 
subject in 1885. Altogether some sixty or seventy papers have al- 
ready appeared in print dealing with the subject as a whole, or with 
certain phases of it. Gallaud (6) has given a very good historical 
r6sum6 of the work done on mycorhizas up to 1904. It will therefore 
not be necessary to go into details here. Gallaud recognizes three 
periods iif the study of mycorhizas. The first of these extends from 
1840 to 1885. During this time several authors noted the presence 
of fungi in connection with the roots of various plants, but with very 
few exceptions they made no special study of them. The second 
period extends from 1885 to 1894, and its beginning is marked by 
Frank's work. Frank was really the father of mycorhiza study. He 
first demonstrated the true morphological nature of ectotrophic 
mycorhizas and applied the name to them. He also advanced the 
hypothesis that the fungi in question are symbiotic with the roots of 
the higher plants. Under the influence of this new idea numerous 
investigators attempted to verify or refute Frank's work, but with little 
success. During the third period, from 1894 to 1904, the important 
papers were mainly of two kinds, systematic and cytological. The 
systematic papers did a great deal toward extending our knowledge 
of the distribution of mycorhizas, while, in connection with these, and 
* Contribution No. 144 from the Botanical Department of the University of 
Michigan. 
[The Journal for January (i: 1-50) was issued 21 F 1914.] 
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