DEVELOPMENT OE THE PERITHECIUM OF M ELIO LA. 
585 
the apex being, as a rule, evenly rounded : the cross-septa dividing the hyphae into 
cells are firmly marked, thick, and dark-coloured like the outer walls. 
The main branches of the mycelium all present the same general characters described 
above. In many cases, however, the blunt apices of the larger hyphse, instead of 
being evenly rounded, become curiously deformed by an accumulation of abnormal 
growths, of the nature of caps (see Plate 43, fig. 7) fitting roughly one over the other: 
these consist of swollen, more or less cuticularised thickenings of the cell-wall, with 
or without granular debris between the layers. They are evidently produced by 
irregularities in the forward growth of the hypha : in the moist intervals the growing 
apex, more delicate than the older portions of the hypha, creeps along the surface of 
the leaf in the normal manner; during recurrent dry and hot unfavourable periods, 
however, sudden hardening and stoppage of growth causes the accumulation of the 
caps. That unfavourable intervals in outward circumstances may produce such abnor¬ 
malities is well seen in the Saprolegnice, and I have in these observed the formation 
of successive shell-like caps of dense cellulose, more or less altered, and enclosing 
granular matter between the layers : the caps are coloured blue by solution of zinc- 
chloride and iodine, the granular debris yellow. These phenomena were by no means 
uncommon with the hyphse of Adilya and Saprolegnia grown, in summer, too long in 
the same water ; of course the pathological changes are produced by different causes in 
the two cases.'" 
Besides the main branches of the mycelium, certain small pyriform or flask-shaped 
outgrowths are given off at pretty regular intervals from the cylindrical cells of the 
larger hyphse (see Plate 42, fig. 2, and Plate 43, figs. 3 and 4) : in some cases each 
cell or joint gives off such a short bran chi et from each side, in others from alternate 
sides. More rarely they are absent altogether. In all cases examined the short 
lateral branchlet arises as a simple bulging out of the lateral wall of the cell : as this 
proceeds, the bud (as it may be considered) swells out, and its cavity finally becomes 
separated from that of the parent branch by a firm septum. The long axis of the 
bud-like protuberance is very generally, though not always directed at an angle of 
nearly 45 degrees with that of the portion of the main hypha lying nearer the 
growing point (see Plate 42, fig. 2, &c.) : its walls are similarly dark coloured and 
firm, and it contains fine grained protoplasm much as the cells of the main hyphse. 
Morphologically considered, the short lateral outgrowths are undoubtedly of the 
nature of arrested branches. 
In one form of Meliola, growing on the leaves of a species of Convolvulus, I have 
observed a second form of the lateral branchlet (see Plate 43, fig. 4), co-existing with 
the commoner pyriform type. In this case the outgrowth was longer, narrowed into a 
sort of neck, and presented the general shape of a Florence flask, seated with its 
bulged out body on the parent branch. In some specimens, each cell of the latter 
* There seems reason to believe that further investigation may throw light on this subject in con¬ 
nexion with the apposition of the cell-wall. 
