Orchid Mycorrhiza. J. Ramsbottom. 4I 
Digestion eventually takes place in all the more deeply lying 
cells, while the external layers act as host cells. The fungus can 
pass out of the protocorm by way of the hairs present on its 
surface. 
This application of the theory of phagocytosis is a most 
attractive one. Gallaud* first suggested the similarity of the 
function of the digestive cells and that of phagocytes, but it is 
to Bernard that we owe the working out in detail}. Much in- 
vestigation on the germinating seed is still needed. Bernard’s 
account of the distribution of the phagocytes is not satisfactory. 
As the photomicrographs (Figs. 10, 12, 13) show it is not unusual 
for all the infected cells of the protocorm to be able to digest 
the fungus eventually. 
GERMINATION WITHOUT FUNGUS. 
How far is it possible to replace the fungus by artificial con- 
ditions? Bernard concluded from a consideration of the way 
in which the endophyte can act at a distance, i.e. bring about 
changes in cells to which it has not access, that there is a general 
modification of the physico-chemical properties of the sap which 
can reach all the tissues. He tried the effect of solutions of salep 
and saccharose of increasing concentrations on seeds of bletilla, 
Cattleya and Laelia. In Bletilla where, as we have seen, ger- 
mination takes place with the formation of slender seedlings in 
the absence of fungi, in high concentrations most of the seedlings 
showed thickened protocorms and short internodes comparable 
with fungus infected individuals. The seeds of Cattleya and 
Laelia at low concentrations swell and become green. With 
higher concentrations development is always much slower and 
more irregular than with fungi, but one can obtain seedlings of 
quite normal appearance. As the concentrations increase the 
development is increasingly better, but more irregular: but there 
is an upper limit beyond which there is no germination. 
Thus it appears that augmentation of the culture medium 
can, in certain cases, supply the place of fungus action. In fact 
Bernard states that in the condition of his experiments it was 
more certain and easier to germinate certain seeds by the action 
of concentrated solutions than to have recourse to fungal in- 
fection. Germination was slow, but very regular, the protocorms 
had a normal appearance and the seedlings when fairly developed 
could be transplanted. Experiments showed that Rhizoctonia 
was able to increase the concentration of the solutions in which 
* F. Gallaud, Etudes sur les mycorrhizes endotrophes. Rev. Gén. Bot. 
XVII, pp. 5 et passim (1905). 
+ Bernard (1911) also showed that the bulbs of Loroglossum contain a diffu- 
sible substance which has a fungicidal effect on Rhizoctonia. 
