Two New Basidiomycetes. H. Bourdot. 51 
diameter as the basidia and projecting 25 to 30. After some 
months growth, the fungus may, by the joining up of several 
patches, cover a wide area; then the central part becomes 
atrophied and finally disappears while the peripheral parts, on 
the contrary, thicken, acquire a purple tint, and tend to turn 
up at the edges which become covered with hairs; the hymenial 
fusiform cystidia are replaced gradually by vesiculose cystidia 
which rise from the sub-hymenial region. 
On the other hand there are species with such a tenuous 
poorly developed appearance that they would be taken either 
for stunted specimens or for the early stages of more robust 
forms analogous to those mentioned above. They are, however, 
fully developed and will always be found in this form. The 
best instance is Peniophora accedens Bourd. et Galz. a small 
furfuraceous patch of a few millimetres, barely visible to the 
naked eye, which may easily be taken for dust covering pieces 
of old wood. We expected to find this plant develop after the 
manner of Peniophora glebulosa or like an Odontia, but for four- 
teen years the gatherings of this minute Peniophora, which have 
numbered hundreds, and have been made in districts widely 
apart, have never shown greater development, and in all its 
characters there is such remarkable constancy that one is forced 
to the conclusion that such forms, until proof to the contrary 
is brought forward, must be described as autonomous species. 
There is much to be done in this part of Mycology which has 
been for a long time neglected. These examples are enough to 
show that it is often more important to observe the living plant, 
than to seek among herbarium specimens for the characters of 
new species. 
The Corticium that Mr Pearson has found was in a luxuriant 
state of vegetation, occupying the whole of the interior of a 
pine log rotting on the ground. It was, however, barely visible 
to the naked eye; it is a ceraceous-pruinose efflorescence, which 
carpets the narrow interstices which are found between the 
fibres of wood attacked by Merulius himantioides Fr. In the 
dry state, when looked at with a magnifica- P 
tion of about 80 diameters, only a fine net- (4 ( ef 
work can be observed, fairly regular and made 
up of white brittle fibres. Its subnavicular 
spores place it apart from all the ceraceous 
Corticiums, to which one would compare it. 
The only species which has microscopic char- 
acters approaching it is Corticium filicnum 
Bourdot, but this is a common species in 
France, which has never varied its habitat on fern débris and 
from its external characters it is most unlikely that any true 
4—2 
Fig. I. 
Cortictum Pearsonit. 
