SYMBIOSIS OF PHANEROGAMS AND FUNGI. 249 
SYMBIOSIS OF GREEN-LEAVED PHANEROGAMS WITH FUNGAL MYCELIA 
DESTITUTE OF CHLOROPHYLL.—MONOTROPA. 
Another instance of symbiosis is observed to exist between certain flowering 
plants and mycelia of fungi, The division of labour consists in the fungus-mycelium 
providing the green-leaved Phanerogam with water and food-stufts from the ground, 
whilst receiving in return from its partner such organic compounds as have been 
produced in the green leaves. 
The union of the two partners always takes place underground, the absorbent 
roots of the Phanerogams being woven over by the filaments of a mycelium. The 
first root that emerges from the germinating seed of the phanerogamie plant 
destined to take part in the association descends into the mould still free from 
hyph; but the lateral roots and, to a still greater extent, the further ramifications, 
become entangled by the mycelial filaments already existing in the mould or 
proceeding from spore-germs buried there. Thenceforward the connection 
continues until death. As the root grows onward, the mycelium grows with it, 
accompanying it like a shadow whatever its course, whether the root descends 
vertically or obliquely, or runs horizontally, or re-ascends, as is sometimes necessary 
when it happens to be turned aside by a stone. The ultimate ramifications of roots 
of trees a hundred years old, and the suction-roots of year-old seedlings, are woven 
over by mycelial filaments in precisely the same manner. These mycelial 
filaments are always in sinuous curves and intertwined in various ways, so that 
they form a felt-like tissue, which looks, in transverse section, delusively like a 
parenchyma. As regards colour the cell-filaments are mostly brown, sometimes 
they are almost black, and it is rare for them to be colourless. The epidermis of 
many roots is covered as if by a spider’s web, whilst the hyphze form a complex 
tangle of bundles and strands broken here and there by open meshes through which 
the root is visible. In other cases an evenly woven but very thin layer is wrapped 
round the root; and in others, again, the fungus-mantle forms a thick layer which 
envelops uniformly the entire root (see fig. 59). Here and there the hyphe 
insinuate themselves also inside the walls of the epidermal cells, and the latter are 
permeated by an extremely fine small-meshed mycelial net (see fig. 59°). 
Externally the mantle is either fairly smooth and clearly marked off from the 
environment, or else single hyphz and bundles of hyphe proceed from it and 
thread their way through the earth. When these branching hyphe are pretty 
equal in length they look very much like ordinary root-hairs. And they not only 
resemble them, but assume the function of root-hairs. The epidermal cells of the 
root, which would in an ordinary way act as absorption-cells, being inclosed in the 
mycelial mantle cannot exercise this function, and have relegated the business of 
sucking in liquid from’ the ground to the mycelium. The latter undoubtedly acts 
as an absorptive apparatus for the partner on whose roots it has established itself; 
and the water in the soil, together with all the mineral salts and other compounds 
