530 Lewton-Brain . — Cor dy ceps ophioglossoides ( Ehrh .). 
or single hyphae (Fig. 31). These do not agree in any 
way with the description and figures given by Reess of his 
haustoria. 
If these three forms of mycorhiza are really due to the 
action of one Fungus, and this certainly appears most prob- 
able, it would seem to show that Elaphomyces variegatus 
is capable of varying its method of attack, according to the 
strength of the root attacked ; when this is small, with thin- 
walled cortical parenchyma, we may suppose the intercellular 
network is sufficient for the destruction of the cortex. On 
the other hand we must presume that the older roots had not 
been attacked until the cortical cells had thickened their walls, 
in which case the formation of the intercellular network was 
not possible or not sufficient, and so the Fungus resorted to 
the intracellular method of attack. I offer this merely as 
a suggestion ; it may be, of course, that three distinct Fungi 
were present. 
In conclusion I have to thank Prof. Marshall Ward for his 
kindness, not only in giving me the material with which to 
work, but also for his assistance while the work was in progress. 
I have also to thank Mr. R. H. Biffen for much advice and 
assistance. 
