412 
Journal of Agricultural Research 
Vol. XXX, No. 5 
the peri dial branches break away, ex¬ 
posing the spores tangled in the gleba. 
The peridial branches are first grayish 
in color and are scarcely to be dis¬ 
tinguished from the rest of the young 
fruit body. As soon as spores are 
formed the head becomes ash-gray or 
cinereus. It is not difficult to deter¬ 
mine by the change in color of the head 
when the first basidiospores are formed. 
As noted previously, the peridium is 
composed of sporophytic hyphae. This 
is proved by the fact that clamp con¬ 
nections regularly occur on these 
hyphae. In a culture bearing only 
conidia one looks in vain for such clamp 
connections, but as soon as the whitish 
flecks or mounds of mycelium develop 
on the conidial layer of the gameto- 
phytic mycelium, clamp connections 
can be found on those hyphae con¬ 
nected with the white mycelium above. 
The contrast between the coarse brown 
mycelium of the Rhizoctonia stage 
of Corticium vagurn and the delicate 
whitish sporophytic hyphae bearing 
basidia is not greater than is found in 
the two stages in the life history of 
Pilacre. 
Brefeld (7) drew his figures of hyphae 
bearing basidia and basidiospores from 
fruit bodies developing on bark. He 
germinated these spores and obtained 
cultures which produced only conidia. 
Later (8, p. 164) he reports producing 
the complete life cycle from basidio¬ 
spores in culture. While these figures 
were drawn with the same care which 
he always gave to the details, when it 
comes to interpretation of his findings, 
he is moved to magnify similarities and 
to discount differences in comparing 
the basidia and their spores with the 
conidiophores and their conidia. As 
noted above, believing that a proto- 
basidium is derived in the process of 
evolution from a conidiophore becom¬ 
ing septate or reduced to a definite 
structure with ultimately four cells, 
each cell producing a single spore, he 
says that the basidiospores and the 
conidia of Pilacre are about the same 
size, differ only a little in form, arise in 
exactly the same w^ay, germinate 
exactly alike, and produce identical 
mycelia. In reality, the conidia and 
basidiospores are very different in color, 
they are absolutely dissimilar in form 
and are borne on hyphae with entirely 
different characteristics and origin. Of 
course the mycelium that develops from 
a germinated basidiospore could not 
differ from the mycelium which devel¬ 
ops from a conidium, both structures 
being gametophytic. Hyphae giving 
rise to basidia are snow white, of deli¬ 
cate proportions, have clamp connec¬ 
tions and sterile tip branches which 
take part in the formation of the “ perid- 
^ 10 .’' Clamp connections are now 
looked upon as an indication of the 
sporophytic condition of a mycelium. 
The recent work which has been done 
on the development of mushroom 
fruiting bodies from two strains of 
mycelium shows that in certain cases no 
clamp connections are formed in cul¬ 
tures from a single strain, but when two 
strains properly chosen are grown 
together so that anastomoses can occur, 
one begins to find clamp connections, 
and later the mushroom fruit body will 
develop. In such forms the binu¬ 
cleated condition of the hyphal cells is 
supposed to arise only along with or 
after clamp connections are developed. 
The presence of clamp connections 
on hyphae is commonly accepted as an 
indication that the fungus belongs in 
the basidiomycete line, but failure to 
find such structures does not mean that 
the fungus must be excluded from this 
group. For example, Gilbert {20) did 
not find clamp connections on the 
hyphae of Dacryomyces. Here in some 
way, not determined, either as the 
result of anastomoses or by division of 
the nuclei, the cells below the hymen- 
ium become binucleated. After fusion 
of the two nuclei in the young basidium 
and the reduction divisions which fol¬ 
low, two of the four nuclei degenerate 
so that only two basidiospores are 
developed. Juel {21) as the result of 
cytological studies of Stilbum vulgare 
Tode believes that the fungus is a true 
Basidiomycete. He finds no clamp 
connections. On the other hand, the 
spores are regularly formed on club- 
shaped structures which originate as 
binucleated cells. The two nuclei then 
fuse. The fusion nucleus divides once 
and before the second division occurs a 
septum is laid down so that the 
basidium becomes 2-celled with one 
nucleus in each cell. The second divi¬ 
sion now occurs, but one of the daughter 
nuclei in each cell degenerates, so that 
only two basidiospores are developed. 
Juel points out that Pilacre and Pila- 
crella are angiocarpous while Stilbum is 
gymnocarpous. The peridium or cover¬ 
ing surrounding the fertile tissue in the 
first two forms is of the simplest 
character. 
According to Brefeld’s figures, one 
can see that the conidia vary consider¬ 
ably in shape and size, some being long 
and narrow, others oval or nearly 
spherical. Some are exceedingly small, 
others very large. Lack of uniformity 
in shape and size is as striking as in case 
of the conidia of Cladosporium, for 
example. The conidial stage of Pilacre 
is to be looked upon as a separate and 
distinct spore form in the life history of 
