DEVELOPMENT OE THE PERITHECIUM OF MELIOLA. 
595 
After a few radial, vertical, and horizontal walls have been formed, tangential 
septa (fig. 42, cl.) make their appearance cutting out series of cells which are to form 
the outer walls, and which become firmer and more deeply coloured, from an inner cell 
mass which gives rise to the ascogonium much as before. Only a few asci are formed, 
in each of which arise eight small oval uniseptate spores, which acquire a pale brown 
colour as they ripen (fig. 42, /., and Plate 42, fig. 43). 
The mature perithecium is shaped like a pear or top, the broad end attached to the 
hypha by a short pedicel, the narrow free end, or apex, becoming thin and diffluent in 
order to allow of the escape of the spores (fig. 43). Very few or no setae are formed 
around the perithecium, and these of the same simple type as those scattered on the 
mycelium (Plate 42, fig. 41). The whole structure of the fruit-body is, therefore, 
much simpler than that of the above described forms, and, from the semi-trans¬ 
lucent characters of the thinner cell-walls, allows the main details to be made out by 
optical sections only. In some of the dark-coloured cells of freshly prepared specimens, 
a bluish tint is often observable ; I have not seen this in any other similar form. 
In no case have I succeeded in tracing a distinct alterative or destructive action of 
the Meliolcis on the cells of leaves to which they are attached. In many instances, 
as, for example, thick leathery leaves like those of Memecylon capitellatum, &c., the 
haustoria seem to have no function beyond that of holdfasts ; in others, such as 
Pavetta, Triumfetta, &c., attacked leaves certainly suffer from the presence of the 
fungus. Nevertheless, I cannot trace this to any direct action of the mycelium ; the 
contents of the cells show no effects which can be regarded as due to the fungus 
mycelium directly. We must conclude, therefore, that where the life of the leaf is 
interfered with at all, it is indirectly ; the dense crust of a well-developed Meliola no 
doubt obstructs the play of physiological functions in an obvious manner, by obscuring 
it from light, blocking up stomata, &c. 
It is now possible to consider the question of the systematic position of these 
remarkable and interesting fungi. Bornet,* following Fries and Leveille, places 
Meliola near the old group of Sphaerias, with especial reference to Erysiplie. I have 
[ already quoted the view of Fries that the Meliolcis may be considered tropical repre¬ 
sentatives of our Erysiphece, and Berkeley! takes the same position. These opinions 
appear to have been based simply on the resemblance in habit and the more obvious 
anatomical characters, and on the fact that no Erysiplie is known in the tropics. 
The detail of structure, and especially of the development of the fruit-bodies above 
described, enable us to criticise these views from a somewhat firmer standpoint. 
Apart from minor points of resemblance between Meliola and the typical Erysiphece, 
such as the haustoria (not well developed in Meliola), the asci, &c., there can be no 
question as to certain points of agreement in the structure and development of the 
I perithecia ; nevertheless, the origin of the fruit-body in the two groups is not obviously 
similar, and at first sight the differences may seem greater than they really are. 
* Op. cit., p. 266. t Introd. to ‘ Crypt. Bot.,’ p. 275. 
