A TOADSTOOL—ITS FUNCTION AND FORM 11
'natural' assemblages of fungi. We know at least three series
in each of which the genera look as if they are reasonably
clearly related, but in each of which there is an agaric at one end
of the series, a thorough-going polypore at the other end and
an alveolate form or one with anastomosing gills some way
in between. These series (Fig. 6) are as follows :—
1. Mycena—Phacomycena—Myccnoporclla
2. Paxillus—Phylloporus—Boletus
3. Schizophyllum—Lenzites—Polyporus (leathery species)
With any such series there arises the question : In what direc-
tion should the series be read? And it does not follow that
because one series should certainly be read in one direction, the
others should be read in the same direction. On the whole,
however, it is easier to picture the polypore habit developing
from the agaric than the reverse, and if there is greater
efficiency in the polypore arrangement this should argue for
selection in that direction.
Perhaps with all this geometry spiced with phylogeny we are
getting away from reality, but it is so tempting to treat a struc-
ture of such regularity as a toadstool in a mathematical manner
and it is difficult to exclude evolutionary ideas from biological
speculation. However, the picture I want to leave you with is
solid and real enough. It is the picture of a toadstool as a
closely co-ordinated mechanism of spore production and
liberation.
Finally let me thank you for bearing with a mycological
president for three whole years, and at the same time let me
express the hope that for many years to come we may have the
opportunity of foraying together amongst the fungi in the
beautiful Forest of Epping.