1922] RAYNER—NITROGEN FIXATION 227 
the products of photosynthesis, but in the nonchlorophyllous 
forms, such as Neottia and Corallorhiza, this is not so, and, on the 
observed facts, the mutual relationship appears to be one of 
parasitism on the part of the green plant. Indeed this condition 
has fully been demonstrated for Gastrodia elata, a remarkable 
non-chlorophyllous species found in Japan. It is certain, therefore, 
that one at least of the so-called “‘saprophytic”’ orchids is parasitic 
upon a fungus, Armillaria mellea, and that the establishment of this 
relation has become obligate for the full development of the plant. 
This is the more interesting in that the fungus concerned is para- 
sitic in habit and invades the tuber of the orchid in the first instance 
in exactly the same manner as it attacks the tubers of potato, upon 
which it is commonly found as a parasite in Japan.? In orchids 
the fungi endophytic in the roots do not spread into the chloro- 
phyllous tissues, nor is there any evidence that they can use atmos- 
pheric nitrogen. 
In Calluna the evidence as to exchange of food materials between 
the two partners may be summarized as follows. There is no 
indication of digestion of mycelium by the root, nor are there any 
obvious symptoms of attack or defense beyond the fact that hyphae 
effect an entry in the first instance and spread from cell to cell. 
That this vegetative activity depends upon a supply of food drawn 
from the plant cells rather than from organic compounds in the soil, 
is suggested by the normal behavior of the symbionts when grown 
in solutions of inorganic salts in pure culture. In the shoot, 
active mycelium is not readily demonstrated although widely dis- 
tributed in a reduced condition; active hyphae occur in the exten- 
sive air spaces of the leaves, and grow into the air from the surface 
of the shoot. Moreover, there is evidence that mycelium under- 
goes digestion by the mesophyll cells of the leaf, and also that the 
fungus can hydrolyze arbutin outside the plant (RAYNER, loc. cit.). 
With respect to nitrogen assimilation, there is cumulative evidence 
that the endophyte of Ericaceae can utilize atmospheric nitrogen 
in greater or less degree, and it is the purpose of this paper to 
present this as briefly as possible. 
* Kusano, S., Gastrodia elata and its epee association with Armillaria 
mellea. Jour. C oll. Agric. Tokyo 4:1-66. 
