406 BULLETIN OF THE BUSSEY INSTITUTION. 
cell-wall is a dark or purplish brown, and in most of the cells there is 
a comparatively large-sized oil globule. These hyphz branch in all 
directions, and the cells of the branches grow constantly longer, 
narrower, and paler, although, in all cases, retaining a tinge of 
brown. The relation of the mycelium to the stellate hairs and outer 
part of the twigs and leaves is clearly seen in cross sections. ‘The 
hyphe run along the surface of the epidermis and of the hairs, which 
it will be remembered resemble a broadly-opened, short-handled para- 
sol. They are twined closely round the stems of the hairs, so closely, 
that the fungus cannot be removed without tearing them off. They 
do not enter into the cells of the olive, and there are no haustoria 
as in the case of some of the leaf parasites belonging to the Hrysiphet. 
Occasionally there are little knob-like projections of the cells which 
seem to indicate haustoria; but, by the most careful examination which 
we have been able to make, we have not been able to see that they 
enter into the cells of the stellate hairs or epidermis and act like 
haustoria. The surface of the hairs and epidermis, however, seems 
covered with a sticky substance (of which we shall have more to say 
hereafter), to which the hyphez closely adhere. Plate 1, Fig. 2, shows 
one of the stellate hairs seen from below, with a portion of the myce- 
lium growing upon it. 
Various modifications of the mycelium are found principally on that 
portion growing on the outer part of the stellate hairs exposed to the 
air. After reaching a certain stage of development, they grow together 
in such a way that the hyphz coming together laterally form a sort of 
membrane, as shown in Plate 1, Fig. 1,d. This membrane is composed 
of only one thickness of cells, but is very uneven as it follows and con- 
forms to the inequalities of the hairs. Its general direction is parallel 
to the surface of the leaf or stem on which it is found. 
Conrpra. — The hyphe, at their free ends, branch in all directions, 
and bear reproductive bodies of several kinds. The simplest form is 
that shown in ‘Plate 1, Fig. 3,d, where the ordinary cells of the myce- 
lium divide by cross partitions into two parts, which do not respectively 
grow to the same shape as the mother cell, but remain together two 
by two, as shown in the figure; the hypha becoming zigzag by the 
alternate lateral displacement of the pairs of cells, which finally drop 
off and readily germinate, each cell producing a germinal tube. In 
other parts of the mycelium, the terminal cell of certain threads di- 
