i95 
an endophytic member of the Erysiphaceae . 
endophytism serving to meet the need of the fungus to shelter its mycelium 
in the early stages of the conidial condition from dry burning winds or hot 
sun, or being due to the inability of the fungus to pierce the thick cuticle 
of xerophytic plants for the formation of haustoria, and the consequent 
need to enter the plant in order to obtain nourishment 1 . It must be noted, 
however, that in a few cases O. taurica is found on leaves possessing a cuticle 
which other members of the Erysiphaceae are able to pierce, thus both 
O. taurica and E. Cichoracearum are found on Verbascum Lychnitis and 
V. phlomoides. 
The fact of the occurrence of an endophytic member of the Erysi- 
phaceae must be remembered in future when discussing the significance 
of the case of induced endophytism under cultural conditions of a normally 
ectoparasitic species (. Erysiphe Graminis DC.) which I have lately re- 
ported ( 4 ). 
A very interesting fact is the possession by Oidiopsis and Phyllactinia 
of certain well-marked characters common to both. We find in these two 
genera the following characters marking them off from the other genera of 
the Erysiphaceae : — a hemi-endophytic superficial mycelium ; lateral appres- 
soria-like organs on the superficial mycelial hyphae ; conidia distinguished 
by their large size 2 , the nature of the epispore, and variability in size and 
shape; and finally, as is noted below (p. 197), the production on certain 
hosts of a well-marked variety showing constant and distinctive morpho- 
logical characters which are very similar in both species. 
These points of resemblance would seem to show either that Oidiopsis 
and Phyllactinia are related phylogenetically, or that they have each been 
modified in the same direction under more or less similar conditions. 
We will now consider the variation in shape and size which is shown 
by the conidia. As can be seen by reference to Plate XIV, the conidium is 
sometimes cylindrical with rounded ends, 50-80 x 12-20 [i ; more often it 
is ovoid, oblong, or subcylindric, often distinctly narrowed and more or less 
sub-acuminate towards the apex, 35-82 x 13-23 fx ; or it may be broadly 
oblong, and rounded at both ends, 38 - 5 ox 20-28 /u. Very rarely the coni- 
dium is quite small, oblong and rounded, truncate at both ends, and 
measuring only 22-32x13-1 6 ft. It is very probable that the great 
differences in shape and size shown by the conidium, even on the same 
host-plant, may to a certain extent be correlated with the position of the 
conidium on the conidiophore. The first conidium produced on the main 
axis differs probably from those subsequently produced, and both of these 
1 Maire (6) remarks : 1 Le mycelium endophytique n’est qu’une adaptation a un hote xerophyte 
et a un climat sec.’ 
2 The large size of the conidium is perhaps due to the need of the germ-tube to be provided 
with sufficient food-material to enable it to grow on the surface of the leaf until it finds a suitable 
stoma to enter. Very probably the germ-tube requires to form one or several appressoria before it 
enters the stoma. 
O 2 
