121 
becoming visible. Not until ten or fourteen days after inoculation, 
when the.leaf had become brown and withered, did transparent points, 
which were most numerous along the nerves and less so upon the leaf 
surface, make their appearance. These points represent pycnidia, which 
are altogether different from those of Cytispora. They are situated un¬ 
der the epidermis, which they push up while their bases are more or 
less immersed in the leaf tissue. At the apex of the swellings the 
epidermis ruptures, forming an irregular roundish opening through 
which may be seen the ostiolum of the pycnidium, which will be de¬ 
scribed in detail below. The pycnidium is flattened and lenticular, yel¬ 
lowish in color, except the ostiolum, which is dark brown. Its walls, 
unlike those of the Cytispora (Fig. 11), are of a pronounced pseudo- 
parenchymatic structure. They are clearly composed of two layers, the 
outer consisting of from one to three rows of flat cells with brown con¬ 
tents. Brown hyphse usually originate from many of the superficial 
cells. This layer has a special structure at the apex of the pycnidium. 
It becomes much thicker and its cells take a radial direction, lying par¬ 
allel to each other and forming papiilse-form projections on the surface. 
The papillse are surrounded by a chaplet of long four or five-celled 
hyphse, which arise from the outer cell and project beyond the epider¬ 
mis. On account of the radial arrangement of the cells at this place 
the opening of the pycnidium will depend upon its time of maturity, 
since the cells are easily pushed apart. There is, therefore, here a simi¬ 
lar arrangement to that in Discula platani. 
Within this is a second layer of somewhat polygonal colorless cells 
which are flattened on the outside, but are more isodiametric within. 
The farther they are situated toward the interior the smaller their lu- 
mina. This layer bounds the cavity of the pycnidium, which is, however, 
very irregular, since the inner layer sends complex projections into it 
from all sides. From these, large round cells filled with dense contents 
arise everywhere. They are the basidia, but they do not form a contin¬ 
uous hymeuial layer. They cut off oval (often rather cylindrical) uni¬ 
cellular colorless spores that measure 6-9 by 3-5//. 
These pycnidia are strongly characterized by the structure of their 
walls, and more especially of their apices, and the form of their basidia. 
Since little stress is laid upon these characteristics in systematic works, 
it was impossible to classify it in any existing genus. It would be 
superfluous to establish a new one, since in all probability it is oidy a 
stage in the life history of Fenestellaplatani. 
Since the culture of these pycnidia in nutritive solutions was unsuc¬ 
cessful (concerning which more will be said) many questions relative to 
their development must remain unanswered. The youngest stage ob¬ 
served consisted of a knot of numerous coarse liyplne (Fig. 12). It 
appears to originate from the Cytispora , although it is noticeably differ¬ 
ent from the beginnings of the Cytispora pycnidia. The number of 
hyphae is smaller, but the hyphse are proportionally stronger. Unfort- 
