Bulgaria poly morpha^ Weil. 133 
development is to a great extent carried on under the bark 
of the trees they grow on, while in the higher forms of the 
Discomycetes the apothecia are always formed superficially 
on the substratum. It is conceivable therefore that some 
such development has occurred as an aid to spore-distribution, 
the flattened exposed disc offering far greater facilities for 
dispersal than the almost closed and sunken perithecia. 
On the other hand, in our ignorance of the phylogeny 
of the Ascomycetes, we may speculate as to whether the 
Sphaeriaceae have not developed in the opposite direction 
also, with the result that the perithecia with partially sup- 
pressed walls have become completely enclosed in the 
stroma. Such a structure would, be very like those we meet 
with in the Tuberaceae. 
