56 
our experiments would meet with negative results. The evidence rather 
points towards discarding the idea that Gloeosoporium nervisequum has 
no other stages in its life history. 
It has not yet been possible to find out these other stages 5 the cult¬ 
ures could not be carried far enough, and forms that might belong to 
the Gloeosporium were found in the open air on fallen leaves and dry 
branches, but we were not able to establish the connection. One form 
which we especially suspected of organic relationship, on account of 
its morphological evidence, is described in detail in what follows. 
II. Discula platani, (Pk.) Sacc. 
Upon Platanus trees attacked by Gloeosporium there are many dry 
branches of the previous year’s growth, which died after all the leaves 
had fallen, and before the close of the vegetative period. Upon these 
are usually a large number of small pustules which finally split 
open. At first they look very much like lenticels, and can scarcely be 
distinguished from them by the naked eye 5 but when one of these 
twigs is moistened small yellowish columns emerge from all the open¬ 
ings; these columns are composed of spores, and show the presence of 
a fungus. 
The structure of the fungus may easily be studied in a cross-section 
of the branch. The young pustules are filled with a pseudo parenchy- 
matic tissue which rests upon the green part of the bark and penetrates 
it slightly. Above (by above is meant the side turned away from the 
twig) the fungus pushes up the bark until it finally bursts (Fig. 3). 
The tissue is then in the form of a cone. The basal cells are nearly 
isodiametric and polygonal, but the upper ones are elongated and lie 
more or less parallel. The point of the cone does not project beyond 
tlTe bark, and the hyphte are more apt to swell up when they reach the 
surface. The entire cone shows a strong upward growth which has its 
origin in the lower cell layer. This layer has here the function of 
meristem and pushes up other portions of the cone by the elongation of 
its cells. 
In more advanced stages pseudo-parenchyma is also developed in 
the uppermost layer of bark parenchyma whose cells have been com¬ 
pletely destroyed. A cavity quickly arises in the cone by the cessation 
of growth in the central part (Fig. 4). Hyplue very quickly grow out 
into the cavity from all sides and clothe it with a hymenium which 
produces spores by successive abscision. The cavity enlarges especially 
towards the surface; the remains of the parenchyma together with the 
cone above them are pushed up considerably, enlarging the slit in the 
bark. The liyphm forming the cone generally become completely ob¬ 
literated ; very rarely only a pore is formed therein; by these processes 
the hymenium is exposed. The outer portions become-dark colored and 
the entire pustule is more or less bowl-shaped (Fig. 5). 
The basidia are unbranched, slender, and cylindrical. The spores are 
