354 Groom. — On Thismia Aseroe ( Beccari ) 
growth of the hyphae, as there are indubitable proofs of the 
influence of the hyphae in leading to an increase in the size 
and staining powers of the nuclei. So there is no reason 
to doubt that the symbiosis in the mediocortex of these 
plants has the same significance as in Thismia. 
To sum up, then. Although the hyphae of endotrophic my- 
corhiza in the mediocortex die soon , the root (or rhizome) cannot 
he said to act like the digestive organ of an insectivorous plant, 
because the protoplasm of the hyphae is manufactured partly 
at the expense and through the agency of the host ; and, further, 
there is, at present, no direct evidence that the hypha renders 
its proteid contents to the host. 
The second point with reference to Frank’s analogy may be 
now considered. Is the organism (Fungus) completely killed 
by the host (root or rhizome)? The evidence all seems to 
point in the other direction. In all the Orchidaceae and 
Burmanniaceae I have examined, in all the cases of orchida- 
ceous saprophytes investigated by others, and in endotrophic 
mycorhiza generally, it appears that there are in the outer 
layers of the absorbing organ hyphae which live as long as 
the organ itself. They are many of them continuous with 
hyphae entirely outside the host, and extending out into the 
substratum. The number and development of these hyphae 
extending outside the plant varies much in different plants, 
often being inconsiderable (Thismia and some Orchids). It 
seems probable, therefore, that Frank is correct in regarding 
these free hyphae as not of supreme importance in supplying 
nutriment to the mycorhiza, though they often ramify closely 
over dead vegetable fragments (Thismia). In Thismia > in 
particular, the whole surface of the thallus appears capable of 
absorbing liquids ; and here also the existence of a sheath 
renders possible the observation that frequently the free 
hyphae are deserting the host , not entering it, a fact which 
seems to give the key to the puzzle. In all the cases of 
saprophytes with endotrophic mycorhiza which I have ob- 
served, the free external hyphae can be traced continuously 
from the substratum into cells capable of manufacturing 
