THE LIFE HISTORY OF PILACRE FAGINEA (FR.) B. & BR. 1 
By C. L. Shear, Senior Pathologist, and B. O. Dodge, Pathologist, Fruit Disease 
Investigations , Bureau of Plant Industry , United States Department of Agri¬ 
culture 
INTRODUCTION 
Pilacre is a fungus holding an im¬ 
portant place in mycology, primarily 
on account of BrefekTs contribution 
to its life history and relationship. 
We may not agree with him as to the 
lines of evolution which he lays down, 
nor be able to confirm all his work as to 
questions of fact in each case. No 
one, however, has given a finer illustra¬ 
tion of the kind and quality of work to 
be done in support of a theory than 
did Brefeld in his study of tl Pilacre 
petersii B. & C.” The writers have 
followed the life history of this “ prim¬ 
itive basidiomycete ” in pure cultures. 
In addition to confirming in the main 
Brefeld’s work, as far as he was able 
to carry his investigation, the writers 
here give additional information which 
should be helpful in clearing up the 
question of the relationship of Pilacre 
faginea (Fr.) B. & Br. to the great 
groups of fungi. 
Basing his argument on the old 
doctrine that, so far as structures in 
fruiting organs are concerned, evolution 
proceeds from the indefinite to the 
definite, and from larger numbers of 
organs to smaller numbers, Brefeld 
strongly supported the view that the 
basidium with its four spores has de¬ 
veloped as a reduction process from a 
septate conidiophore which originally 
gave rise to an indefinite number of 
conidia. One of his lines of evolution 
runs from the smuts, with their “hemi- 
basidia” and yeastlike budding of 
spores, through the rusts, Auricularia- 
ceae and Tremellaceae with their 
“protobasidia, ” each of the four cells 
producing a single spore, to the auto- 
basidiomycetes of the mushroom type. 
It is in the line of “ Protobasidio- 
mycetes” that Pilacre is brought for¬ 
ward in support of the main argument 
in favor of his theory, namely, that 
basidia and conidiophores, and basid- 
iospores and conidia are, respectively, 
homologous. 
According to Brefeld, the small, 
grayish sporocarps of Pilacre frequently 
found on old beech logs are the equiv¬ 
alent of the ordinary mushroom fruit 
body. In dissecting the fruiting heads 
he found that the spores were formed 
on true basidia. Each basidium had 
exactly four cells and each cell bore 
only one spore. Though recognizing 
the very dissimilar characters of the 
fruiting structure, he places Pilacre 
among the “ Protobasidiomycetes ” next 
to the Auriculariae, but differing from 
the Auricularias in being angiocarpous 
and in having a gleba. The basidia 
were not developed in a definite hy- 
menial layer. 
In Brefeld’s first cultures ( 6 ) 2 ob¬ 
tained by germinating spores from the 
fruiting heads only a hyphomycetous 
conidial form developed. In view of 
the fact that he could find no such 
conidial stage described and had not 
found it in nature he assumed that its 
production was due to the unnatural 
environmental conditions of his culture. 
MATERIAL AND METHODS 
Pilacre faginea has been collected by 
the senior author in localities as 
widely separated as New York and 
Florida. Although it occurs most 
frequently on beech logs it has been 
found on Acer, Carpinus, and other 
hardwoods, and typical specimens were 
found growing in the Florida ever¬ 
glades on wood of some subtropical 
tree. 
The material for the cultures upon 
which the discussion in this paper 
is based was obtained in September, 
1921, from specimens growing on a 
beech log near Chain Bridge, Va., a 
few miles from Washington. 3 Poured 
plates of corn-meal agar were made, 
using spores from the fruiting head. 
Sixteen single spore cultures were 
isolated and grown either at room 
temperature or in the refrigerator. 
Subcultures were grown on corn-meal 
1 Received for publication June 16, 1924—issued May, 1925. 
8 Reference is made by number (italic) to “Literature cited,” p. 417. 
8 The writers are indebted to Angie M. Beckwith for assistance in the culture work. 
Journal of Agricultural Research, 
Washington, D. C. 
( 407 ) 
Vol. XXX, No. 5 
Mar. 1.1925. 
Key No. G-453 
