MICHIGAN ACADEMY OF SCIENCE. 
45 
DEMONSTRATIONS OF EOTGTROPHIC AND ENDOTROPHIC 
MYCORHIZA. 
(Abstract.) 
W. B. MCDOUGALL. 
The study of the mycorhiza of our common forest trees was begun, 
by the author, in July, 1911. The purpose, primarily, was to work 
out the seasonal relations of these mycorhiza, and, if possible, to add 
something to our knowledge of their physiological and ecological rela- 
tions. The work will continue another year before anything like a com- 
plete report can be given. It seems desirable, however, to call attention, 
at the present time, to the following results. 
1. On Caryo ovata three forms of ectotropliic mycorhiza, distinguish- 
able by their external color, and also by their microscopic structure, 
have been found on the same tree. One of these is bright yellow in 
color. The fungus mantle is distinctly, filamentous, and numerous short 
branches extend from it into the soil. A second form is brown. The 
fungus mantle in this case consists of pseudoparenchyma such as is 
found in many lichens. The outer surface is smooth, without any out- 
ward extending branches. A third form, found on Cary a, is whitish 
oi- nearly colorless. The fungus mantle is distinctly filamentous, but 
is smooth on the outside. 
2. On Quercus the same variations in microscopic structure were 
found, but without the variations in color, all specimens collected being 
whitish. 
3. On Larix laricina a form was found in which the outer cells 
of the root cortex are so pushed apart by the growth of mycelia between 
them that some of them are isolated as islands in the fungus mantle. 
4. On Acer saccharinum and Acer rubrum en do trophic mycorhiza 
were found in great abundance. The vesicles described by several 
authors were frequently found in the mycorhiza of the maples. 
5. On Tilia americana specimens were collected in which one and 
the same fungus is both ectotropliic and endotrophic. This novel form 
is hitherto unreported, and may be classified as a heterotrophic my- 
corhiza. 
(Lantern slides and microscopic slides of all forms mentioned were 
shown.) 
