THE ANATOMY OF A MUSHIIOOM. 
391 
the plant is recognised as a vegetative entity is in that of 
‘‘ spawn,” or, more accurately, as mycelium. This mycelium is 
essentially an agglomeration of vegetating spores. It is similar 
to the germinating threads of other fungoid spores ; and to this 
entangled, anastomosing, branching, intricate network of deli- 
cate, slender, colourless threads is given the name of mycelium.” 
A mushroom may, like an orthodox sermon, be treated under 
three heads ; for it resolves itself into three parts, viz., the 
mycelium, the hymenophore, and the hymenium. These are 
represented, in plainer and less technical language, the first by 
the spawn,” the second by the ‘‘ stem and cap,” the third by 
the gills.” 
The mycelium has already been almost as fully described as 
necessary for the present purpose. Its normal form is that of 
branched, slender, hyaline threads, produced by the germination 
of the spores. An abnormal condition obtains in some instances 
in which the mycelium becomes compacted into a solid mass, 
at one time regarded as a perfect fungus, and constituted a 
genus under the name of Sclerotium. It is now admitted that 
a sclerotium is not a complete fungus, but only a compact 
mycelium, which may produce a perfect fungus, as in the case 
of Agaricus tuberosus, Peziza iuherosus and the ergot {Sclero- 
tium clavus), which develops Claviceps purpurea. The my- 
celium of the mushroom does not, as far as we are aware, pass 
from the filamentous into the compact or sclerotioid form. We 
have termed the sclerotium an abnormal condition, which is 
scarcely accurate, since we only know Claviceps purpurea, for 
example, except as developed from this compact kind of my- 
celium; so that the sclerotium must be regarded as the normal, 
and not the abnormal, condition of the mycelium of that fungus. 
The hymenophore is represented in the mushroom by the 
stem and the cap, or pileus, by which it is surmounted. This, 
with the mycelium, constitutes the vegetative system. At certain 
privileged points of the mycelium the threads seem to be 
aggregated and become centres of vertical extension. At first 
only a small, nearly globose budding, like a grain of mustard 
seed, is visible ; but this afterwards increases rapidly, and other 
similar buddings, or swellings, appear at the base. As the 
young “ hymenophore ” pushes through the soil, it gradually 
loses its globose form, becomes more and more elongated, and 
in this condition a longitudinal section shov/s the position of the 
future gills in a pair of opposite, crescent-shaped, darker- 
coloured spots near the apex (fig. 2). In another and still more 
advanced stage the stem distinctly develops with a nearly 
globose head. The dermal membrane, or outer skin, seems to 
be continuous over the stem and the globose head. At present 
there is no external evidence of an expanded pileus and gills. 
