Orchid Mycorrhiza. J. Ramsbottom. 43 
cuspidatum to a remarkable degree, though the favourable action 
was of short duration in the conditions of his experiments. 
GASTRODIA. 
An unusual and interesting type of mycorrhiza occurs in 
Gastrodia elata*, a non-chlorophyllous orchid widely spread 
“throughout Japan, where it occurs mostly in woods under 
Quercus serrata and Q. glandulifera. The full-grown flowering 
tuber is oblong and slightly curved, attaining almost without 
exception a length of 10-17 cm. This tuberous rhizome is the 
whole vegetative part of the plant and consists essentially of 
parenchymatous cells. Multiplication usually takes place by the 
tuber. It produces long rhizomes from its apex or node, upon 
which stalked off-sets are developed. At the end of autumn the 
mother body and the pedicel of the off-set undergo degeneration, 
so that the daughter tubercles are set free. Unless the mother 
tuber has been infected with the necessary fungus the off-sets 
decrease in size with each successive generation, until they be- 
come so much reduced and deficient in food materials that they 
are incapable of further multiplication. The fungus necessary 
for proper development is not a microscopic mould as in the 
other orchids studied, but Avmuillaria mellea, the well-known 
“honey fungus.”’ This toadstool is extremely common in our 
woods where it is a most destructive parasite, ‘“‘indeed more 
trees die, in Europe at any rate, from attack by this fungus than 
through any other parasitic agentf.’’ The fructifications are 
found generally on or near stumps. If the earth beneath the 
toadstool be dug up it will be found to contain one or more black 
strands, resembling bootlaces, which are attached to the base 
of the stem. These rhizomorphs, as they-are called, consist of 
densely compacted fungus mycelium. Further, the mycelium 
in the wood of the tree itself is first felted and grows up through 
the cambium to a considerable height: when the tree is dead 
and the bark has become loosened the mycelium is transformed 
into a tangled mass of flattened rhizomorphs. Early mycologists 
considered that they were here dealing with three different 
species of fungus—the toadstool (Agaricus melleus), the rhizo- 
morph under the bark (Rhizomorpha subcorticalis) and the 
rhizomorph in the ground (Rhizomorpha subterranea). 
It is with the subterranean rhizomorph that we are here con- 
cerned. It forms a cylindrical, smooth, black strand, usually 
I to 1-5 mm. in thickness. Its peripheral portion, the so-called 
cortex, consists of compact, pseudoparenchymatous, brownish 
* S. Kusano, Gastrodia elata and its symbiotic association with Armillaria 
mellea. Journ. Coll. Agric. Imp. Univ. Tokyo, Iv, pp. 1-66 (1911). 
+ W. E. Hiley, The fungal diseases of the common larch. Oxford (1919). 
