291
PRESIDENTIAL ADDRESS
Dispersal in Cup Fungi
BY PROFESSOR C. T. INGOLD, D.Sc.
[Delivered 26 March, 1955]
For many years I have been interested in the question of
the dispersal of spores in fungi, and so I have chosen
to-day to address the Club on an aspect of this
subject.
The Cup Fungi, or Discomycetes, belong to
the Ascomycetes, by far the largest of the four
major groups of fungi. The Ascomycetes are
characterised by the ascus, a special type of
sporangium which normally contains eight
spores. In most species the ascus is explosive.
It is a spore-gun. It finally bursts, squirting
the contained ascospores into the air, usually
to a distance of a centimetre or two (Fig.
1). In those Ascomycetes with explosive asci,
the distance of spore discharge is rarely less than
0.2 cm. and at the other extreme the greatest
range of an ascus is 60 cm. reported for Ascobolus
immersus. It is of interest to compare the range
of the ascus in Ascomycetes with that of the
basidium in Basidiomycetes. This latter group
is the second largest in fungi. The characteristic
feature is the basidium. This is a special type of
sporangium normally producing four spores, but
these are formed externally—not internally as in
the ascus. At maturity, in most Basidiomycetes,
the basidiospores borne on the basidium are

violently discharged. However, the range
of this gun is not nearly so great as
that of the ascus. The distance of basidio-
spore discharge varies from 0.005 cm.
Fig. 1.
Pyronema confluens.
Ascus before and
after discharge.
(X 200.)