1
PRESIDENTIAL ADDRESS
A Toadstool - its Function and Form
BY PROFESSOR C. T. INGOLD, D.Sc.
[Delivered 24 March, 1956]
To-day i have chosen to discuss the function and form of a
toadstool. The first part of my address will be largely
factual and will deal with the fruit-body in relation to its
function. However, in the second part I shall to some extent
leave "the solid ground of Nature" and consider toadstools
from the mathematical or rather geometrical point of view.
By a toadstool I mean a fungus fruit-body with a disc- or
dome-shaped cap held aloft by a central stipe and having its
spore-bearing surfaces displayed underneath on gills (as in
most toadstools), or lining pores (as in Boletus), or covering
spines (as in Hydnum).
Let me remind you that the fruit-body of a fungus, whether
it is of the toadstool type, or a puff-ball, or a woody bracket,
or the apothecium of a cup-fungus, is simply a mechanism
concerned with the production and liberation of spores. The
feeding part of the fungus—the mycelium—lies hidden in the
nutrient substratum such as the wood of a tree trunk or the
humus of the soil. In a toadstool we are dealing with a structure
conditioned by a single function; reproduction ; unlike the shoot
of a green plant which is concerned with two major functions:
food production by photosynthesis and reproduction.
Toadstools belong to the Basidiomycetes characterized by
the production of spores externally on special structures called
basidia. Within Basidiomycetes they are assigned to Hymen-
omycetes in which the spore-bearing surfaces are exposed at
maturity and in which the spores are violently discharged from
their basidia. The basidium is a special kind of spore gun and
its characteristics seem to have had much to do with the types
of fruit-body which have developed in Hymenomycetes.