DEVELOPMENT OF THE PERITHECIUM OF MELIOLA. 
591 
derived from the repeated and rapid division of the cell B, and this view may be 
recommended on the ground of analogies with the Erysiphece, to be examined 
hereafter; hut, while figs. 19 and 20 by no means decide the point, we shall find 
that in the perithecium of another species of Meliola (or an allied form) the con¬ 
struction almost certainly proceeds by continued cutting up and “ delamination ” 
of the results of division of one cell. 
Be this as it may, the young perithecium now consists of the following parts :— 
A central “core” of delicate-walled, colourless or yellowish cells, very rich in finely 
granular protoplasm, and, surrounding this completely, a single layer of cells with 
thick, hard, dark-coloured walls (especially those on the exterior surface) ; the whole 
mass is attached to the liypha from which it originated by a very short pedicle 
or joint (see Plates 43, 44, figs. 19-24). 
At a period slightly later than the above, the cells of the outer layer are becoming 
multiplied by tangential walls, and those of the inner core by radial and horizontal 
divisions : these processes go on for some time, until the whole perithecium is a 
complex of many small cells, the outer of which become firmer and darker-coloured, 
the inner delicate and full of fine-grained protoplasm as described. 
No trace of the internal structure is, however, visible now from the outside. 
On isolating a perithecium at this stage—a matter of no slight difficulty, but 
practicable with a slender knife used under a low power of the microscope—it 
presents the forms shown in fig. 25 (Plate 44), on being rolled over. Above, the outer 
surface curves equally away from the centre, and the slightly projecting walls of the 
cells give it an appearance of being embossed (fig. 25, x.). From below (fig. 25, y ), 
the object looks very different; the surface is much flattened and nearly circular, and 
from many of the cells are processes developing as hyphae in all directions. These 
radiating processes creep close along the surface of the leaf, to which the fruit-body is 
also appressecl, and no doubt serve to give a much firmer hold for the fruit; at first 
their thin walls are only of a pale brown hue, but rapidly acquire the thickness and 
deep colour of the fruit and mycelium. Seen from the side, the young perithecium 
: presents the appearance sketched at fig. 25, z. It is these radiating anchoring hyphse 
which form collectively what Bornet terms the “ receptacle,” and from them, at a 
later period, the bristling setce found around the mature fruit are developed. 
From the stage just described the development of the fruit-body proceeds rapidly ; 
but, since the objects now become of a more manageable size, 1 have been able, by 
actual sections through the perithecium embedded in spermaceti or gum, or, better 
still, in elder pith, to obtain some insight into the processes going on even in the 
centre of the mass of cells. 
At stages just prior to the one last described, the central core of thin walled cells— 
which it will be remembered has been derived from continuous divisions of the cell A 
—is commencing to divide up by septa in several directions (figs. 23, 24), while the 
outer layers surrounding this—derived primitively from B, and, possibly, in part from 
4 G 2 
