774 
Schwartz . — Observations on 
the plant, at times giving rise to its death, and a poor store of reserve food 
such as starch. 
On the other hand, in the case of symbiosis, plants with a symbiotic 
partner ought to, and do, flourish better than those in similar situations 
without a symbiont. This is the case in the Leguminosae, in which plants 
bearing plenty of root nodules, containing the nitrogen-fixing Bacteria, 
thrive better than those with fewer or no nodules on their roots. Again, 
the host plant may provide a special home or region for the use of its 
symbiont ; this, however, may likewise be the case in parasitism, as for 
example oak-galls. We may compare also the root nodules of the Legumi- 
nosae with those of the Juncaceae, the former being a case of symbiosis 
and the latter one of parasitism. With regard to Asarmn , there is neither 
hypertrophy nor destruction of tissue, and the cell nuclei when visible in 
mycorhizal cells are in most cases of normal size and appearance. On the 
other hand, a special region of the root, viz. the innermost cortical layers 
abutting on to the stele, is set apart by the plant for the habitation of the 
fungus, which for its part makes no attempt to stray from this region. In 
the cell layer outside the endodermis, the cells were seen to be filled with 
dead fungoid matter, suggesting that either the fungus was providing food 
for the plant, and the cells contained the undigested residue left after the 
absorption of the digested portion into the stele, or that the fungus was 
a parasitic one which had been killed by this innermost cell layer to prevent 
its entrance into the stele. The position of the fungoid layers close to 
the conducting stele, the similarity of the fungus with its coiled hyphae 
in some cells and irregular dead masses in others to the mycorhizal Fungi 
of Thismia Aseroe , Neottia Nidus-avis , and other roots, are all facts 
which favour the former interpretation. The shade-loving nature of the 
plant, and the presence of humus in the soil, also point to the same 
conclusion. 
It is evident from the deeply seated situation of the fungal home that 
the fungus obtains all its nutriment from the plant, although some of it may 
be in a raw state, unaltered by the plant since its entrance into the root 
from the soil. The carbohydrate is apparently supplied by the reserve 
starch of the root, which is mostly absent from the mycorhizal cell layers, 
or the fungus may feed on the sugars supplied by the green leaves to the 
roots, these sugars being converted into starch in those cells of the root 
which are free from fungus. As far as the facts observed warrant the 
expression of an opinion as to the function of deeply seated endotrophic 
mycorhiza, one is inclined to accept Stahl’s hypothesis that the r61e of the 
fungus is to elaborate the raw salts absorbed from the soil into organic 
compounds such as asparagin, and in this connexion the lack of calcium 
oxalate crystals from Asarum roots is suggestive. The diminished numbers 
of root-hairs on mycorhizal roots is difficult to explain when we have such 
