208 MR. P. GROOM—CONTRIBUTIONS TO THE 
holosaprophytes appears to confirm the theory that mycorhizal 
hyphe exert a beneficial effect on the host, and that the fungus 
is not merely a passive companion. The mycorhizal fungus makes 
its way into parts which are absorbing, whether the latter be 
rhizomes or roots ; further, it avoids the rhizome (including sub- 
terranean scale-leaves) if the latter does not absorb food, though 
the walls of the cells may be as thin or even thinner than those 
of the absorbing-organ.  Galeola javanica and Epipogum nutans 
afford good examples of this. In Galeola the mycorhizal fungus 
penetrates the roots and small parts of the rhizome-axis which 
have hairs; but it does not live in the scale-leaves, although the 
cell-walls of the latter are very thin in places. In Epipogum 
nutans the fungus does penetrate the scale-leaves, and roots are 
absent. In Galeola the scale-leaves do not absorb food; in 
Epipogum nutans they are the only absorbing-organs possessed 
by the plant. Again, in Corysanthes hyphe enter and live in 
the absorbing rhizome-axis, but not in the delicate scale-leaves. 
In Aphyllorchis and Lecanorchis, too, the roots, but not the 
subterranean scales, have mycorhizal mycelia. In particular 
mycorhizal hyphe appear to enter the plant only by cells which 
are specifically absorbing-cells. In Galeola javanica they enter by 
any of the superficial cells; in Epipogum nutans only by the 
long hairs of the absorbing-scales ; and more markedly in the 
rhizome of Corysanthes sp. only the hairs on the multicellular 
protuberances permit the entrance of hyphz; and where these 
are absent, ¿ e. higher up the axis, no mycelia occur in the 
rhizome. Again,inthe green Spiranthes australis, in my material, 
byphe entered only through the root-hairs, not by the ordinary 
cells of piliferous layer. Therefore it seems probable that the 
absorbing-cells exert some chemotropic power of attraction on 
the mycorhizal hyphe. 
One important point suggesting that the mycorhizal fungus 
exerts a beneficial effect on the host is that in the cortical cells 
infected. by mycorhizal mycelia the nuclei grow and become much 
more deeply-staining. In fact, the nuclei of the cells infected 
with the hyphæ remind one of the hyperchromatie nuclei in 
certain vigorously absorbing-cells of animal tumours. 
Finally, in confirmation of the view that the mycorhizal 
fungus is no passive companion, there is the fact that no reserve- 
foods are stored up in cortical cells which contain active mycelia. 
Thus in these infected cells no starch is present, even when it is 
