-1887.| BOTANICAL GAZETTE. 179 
host. In view of the facts, one can be an advocate of the 
algo-fungal theory without believing that there is a double 
parasitism, 
In 18858 Frank announced the following discovery: that 
certain species of trees, especially Cupulifere, do not regu- 
larly obtain their food directly from the soil, but their roots 
are connected with the mycelium of a fungus by whose 
agency all the nourishment is transferred from the soil to the 
ree. He called this condition Mycorhiza, and described the 
fungus as intimately united with the inner cortex of the roots 
just back of the tips and forming a felt-like cap over the tips. 
He maintained that this union of mycelium and roots was of 
constant occurrence in the Cupuliferz which he had exam- 
ined, oaks, beeches, chestnuts, hazel-nuts and hornbeams, 
and more or less constant in Salicaceawe and Conifere. At a 
later date* he went further and stated that the Mycorhiza is 
a symbiotic condition which may perhaps be found in all 
trees under certain conditions ; that itis found only where the 
soil consists of humus or undecomposed plant remains ; that 
the fungus of the Mycorhiza conveys to the tree not only the 
necessary water and the mineral constituents of the soil, but 
also the organic material derived directly from the humus 
and decomposing vegetable matter; and that it is through 
the agency of the fungus alone that the tree obtains its food 
from the soil. If one could accept without reserve the con- 
Clusions of Frank, we have in Mycorhiza a clear case of 
symbiosis in which a fungus which lives as a saprophyte on 
vegetable mould is intimately united with the tissues of Phz- 
hogams on which it acts, not as a parasite but as a conveyer 
of nourishment. Unfortunately, the statements of Frank are, 
to a great extent, not confirmed by other competent ohserv- 
oe. Re. Hartig has shown? that the Mycorhiza condition 1s 
oat all necessary to the nourishment of trees even in Uu- 
Puliferze, since he finds that, in many cases, roots of healthy 
trees are quite free from Mycorhiza, and, even in trees where 
: ere is a marked Mycorhiza of some roots, there are others 
quite free from it. He regards Mycorhiza not as a case of 
Symbiosis comparable to that of lichens, as does Frank, but 
rather a case of proper parasitism, and Kamienski® states that, 
in the cases of Mycorhiza of trees which he has examined, 
h 
© has always found evidences of injury done to the roots by 
Fa ee 
: Ber. Deutsch Bot. Ges. IIT, 128. 
*L e. HI, XXVIL. 
« Bot. Centralblatt, XXV, 350. 
Bot, Centralblatt, XXX, 2. 
