326 Ward. — Recent Publications bearing on the 
Investigation yielded the unexpected result that certain 
trees, especially the Cupuliferae, have almost the whole of 
their root-system covered with mycelium, the fungus being 
associated symbiotically with the root : the conclusion is 
drawn that the fungus-hyphae act the part of the root-hairs 
elsewhere, and that the whole of the absorption from the 
soil is due to their action. 
The younger roots of any oak, beech, hornbeam, hazel, 
or chestnut, at any time of the life of the tree, from any 
of the distant places examined, were found to consist of a 
double structure — the true root as a sort of core, covered 
by a close web of mycelium as an envelope. Such an as- 
sociation of root and fungus is to be named a Mycorhiza . 
In appearance the Mycorhiza resembles some sclerotia, 
the mycelium forming a sort of pseudo-parenchyma, the 
outer walls of which become dark brown as it ages. The 
weft of mycelium covers the root-apex as well as the parts 
behind, and is at first white : even the root-cap is therefore 
covered in. 
The coating of mycelium varies in thickness, but usually 
forms a layer several cells deep. Hyphae dip down between 
the cells of the outer layer of the root proper, and grow 
around them completely ; they do not leave the cell-walls, 
however, and are not found in the cell-lumina, nor deeper 
down in the tissues of the root. These ‘endophytic hyphae’ 
are very much thinner than those outside. 
The outer surface of the mycelial envelope may be clean 
and smooth, and it will be understood that so complete and 
continuous a covering prevents the formation or emergence 
of root-hairs ; in many cases, however, free hyphae develope 
from the outer surface of the mycelial envelope, and radiate 
out into the soil, growing at their ends, and curiously re- 
sembling true root-hairs in many morphological points. 
Frank insists moreoyer that they replace the root-hairs 
physiologically. They become attached to particles of soil, 
and can be the only means for absorbing water and sub- 
stances dissolved in it. Sometimes many of these free hyphae 
