10 
DEVELOPMENT 
appears as if water-logged, and has a very powerful and 
disagreeable smell. The water evaporates, and the peridium 
is filled with a dusty mass of spores and threads ( capillitium). 
This remarkable deliquescence is observable in many 
Gasteromycetes. In certain genera, however, the walls 
of the gleba chambers do not entirely disappear— e.g., 
in the Birds’-nest fungi they thicken, and each chamber 
ultimately remains as a little seed-like body, the peridiolum, 
having its inner cavity lined with basidia and spores. 
In some puff-balls the whole of the interior does not 
become powdery—a thickened cellular portion remains (the 
sterile base). It may be continued downwards as a stem , or 
upwards into the spore mass as a hemispherical pillar known 
as the columella. 
The capillitium threads and the spores of puff-balls can 
be well seen under a microscope with a J-inch objective. 
In some species the stalk ( sterigma) remains for a long time 
attached to the spore. Such spores are termed “ pedicellate.” 
The exoperidium in earth-stars (Geaster) consists of three 
layers: the mycelial (outside), the fibrillose (central), and 
the fleshy inner layer, or collenchyma. 
The mycelial layer is so-called because, in many cases, 
the threads of mycelium which bind the plant to the soil 
proceed from it. In some museum specimens (especially 
G. hygrometricus) this layer is absent (it remained attached 
to the ground when the plant was gathered), and the outer 
peridium in such appears quite smooth. Generally, how¬ 
ever, it remains more or less firmly attached to the middle 
one. In G. fovnicatus it forms a cup at the base of the arched 
segments of the middle layer. 
The middle or fibrillose layer is the thickest, and is often 
the only one present in herbarium specimens. It is very 
variable. In some species it is strongly hygroscopic. When 
the plant is moist the segments are reflexed, but they become 
strongly incurved when dry. This can be easily demon- 
