THE FUNGUS-ROOT (MYCORRHIZA). 185
been brought down by the hooked processes. It is possible to
find scattered portions of the hyphal threads that were around
and between the two styles at different points along the hypo-
cotyl. The fungus is not difficult to identify as such. It has a
diameter of 2 to 2.5μ, is frequently septate, with cells 15 to 18μ
in length. It is stained in a few minutes by a solution of cotton
blue in lactic acid. The fungus has not so far been traced below
the surface of the soil except in small quantity. The occasion
is not opportune to suggest the end of a story, two chapters of
which are not without some importance. The threads are in a
correct position, the hooks are there to catch the threads, and
threads are carried down. One cannot fail to recognise that so
many accommodating conditions are not accidental. The fungus
produces spores while attached to the style. From the shape
and position of these spores it is probable that the hyphal
threads are those of Sporotrichum pulviniforme. More detailed
information respecting the presence of this fungus on the styles
of the birch fruit at the time the fruit falls, awaits further
investigation that is being carried on.
Much has been written respecting the relation between the
higher plant and the fungus that forms the mycorrhiza.
Frank's opinion, as expressed in a paper already cited was,
"that the organic union between root and mycelium, their
harmonious growth and the close physiological relations which
must exist, all point to this being a new case of symbiosis. From
the side of the root we must regard the fungus as a parasite
which takes from the former food-supplies of the nature of carbon-
aceous assimilated material; its minerals, etc., must be taken
by the fungus itself from the soil, the free hyphae acting as root
hairs."
As regards the birch, it may be pointed out that during the
first ten years of its life it grows at a rapid rate, lengthening as
much as 2 to 2.5 feet during the first year. The association with
the fungus would appear to put no check whatever upon the
growth of this tree.
As already stated little was written respecting ectotropic
mycorrhiza until recently. As a result of research opinions are
still not agreed.
Weyland (1912), considers that the fungus in ectotropic my-
corrhiza is really a parasite and has nothing to do with symbiosis.