DEVELOPMENT OP THE PERITHELIUM OF MELIOLA. 
587 
least, they become detached, and act as vegetative reproductive organs or couidia, 
each putting forth bud-like processes which develop into new hyphse. Bornet 
remarked the separation of these buds in Meliola amphitricha, and hints at their 
possibly serving as reproductive bodies much as the Oidium forms of Erysiphece: 
1 since he worked with dried specimens, however, this question could not be decided. 
Bornet remarks that the mycelium on the upper side of many leaves are sterile, 
while those below and protected from the direct rays of the sun alone support 
perithecia: this is certainly not true for the species examined by me, and, indeed, I 
cannot determine any difference between the upper and lower mycelia in this respect. 
Those on the upper surface seem quite as productive of spores, &c., as those below, and 
in many cases— e.g., those Meliolce so common on Memecylon —the mycelium vegetates 
almost exclusively on the upper surface, and is quite fertile there. 
Besides the short pyriform and flask-shaped branchlets described above, the 
mycelium bears certain stiff, upright appendages of the nature of setce (see Plate 42, 
figs. I, 41, and Plate 43, fig. 8) : these setce spring from the cells of the hyphse at 
various points in their course, and, from their position and mode of origin, are probably 
to be regarded, morphologically speaking, as lateral branchlets which become elongated 
in a direction more or less perpendicular to the plane of the leaf. Such a seta grows 
very rapidly and soon reaches its limit: the cylindrical cells composing it are relatively 
longer than those of the hyphse, but resemble them in other respects (the walls being, 
perhaps, somewhat stiffer and more deeply coloured) and taper above, in the simple 
types, or become variously branched. 
In most Meliolas the setce are especially aggregated around the perithecia, forming 
circles of stiff radii springing from what Bornet terms the “receptacle” : they are 
also developed, however, from various isolated points of the mycelium bearing no 
direct relation to the fruit-bodies. 
The forms of the setce vary from a simple, upright or curved filament, to structures 
branched like antlers, trifurcate, twisted, &c., at the tip (cf. Plate 43, fig. 8 and 
Bornet’s figures*) : Bornet has made use of these details in classifying the formal 
| species, and although it is doubtful whether the more similar types are constant, there 
can be no objection to their use much in the same manner as the appendages of Ery- 
siphece, &c., are used to distinguish the forms of that group. Bornet regards the 
origin of the setce at points on the mycelium as marking out places where new 
perithecia are to be developed : I cannot say that this idea is altogether a false one, 
but investigation of the development of the fruit-bodies seems to show that at 
least no necessary connexion exists between the two phenomena. 
As to the function of the setce , little or nothing can be stated. The earlier sugges- 
tions of Sprenuel and Fries (as quoted by Bornet) that they may be organs for the 
exit of the spores cannot be accepted : not only on the ground of the disproportion 
* hoc. cit.. plates 21 and 22, figs. G, 15, 16, &c. 
