2 THE ESSEX NATURALIST
The basidium (Fig. 1) has a development characteristic both
in its cytology and in its morphology, although we shall con-
sider only the latter aspect. It starts as a small club-shaped
cell of the spore-bearing layer (hymenium). From its blunt
apex four little projections (sterigmata) arise and then the tip
of each of these swells up, but in an asymmetrical manner, to
form a basidiospore. At the base of the fully formed basidio-
spore, and very close to its attachment to the sterigma, is a
minute projection or hilum.
Fig. 1. Collybia radicata. Stages in the development of the basidium.
When mature the four spores of the basidium are shot away
in succession with a short time elapsing between the discharge
of sister spores. The series of visible events connected with
discharge is clear. Just before a spore is shot away, a drop of
fluid appears at the hilum, grows to a certain definite size and
then the spore disappears from the sterigma carrying the drop