296 THE ESSEX NATURALIST
spores. A good example is Geoglossum. Several species are
common, growing amongst short grass in the autumn. The
black apothecium is stalked and, instead of being cup-
shaped, takes the form of a club with the hymenium cover-
ing the whole surface. The tips of ripe asci project slightly
beyond the general level of the hymenium. Each ascus
contains eight long septate spores. When mature, the
ascus dehisces by a minute apical pore. Into this a single
spore is pushed, thus stoppering the ascus. It slowly moves
forward, then gathers speed, and is discharged so quickly
that it cannot be seen in flight. A second spore immediately
takes its place as a stopper to the ascus and is in its turn
discharged. So the process goes on until the full comple-
ment of eight has been shot away.
In such an apothecium as that of Peziza or Geoglossum
there are millions of asci, but in some smaller species the
number is very much less. This is particularly true of some
of the tiny species to be found on the dung of herbivorous
animals. If freshly-deposited horse-dung is kept in the
light under a glass cover, a fairly regular succession of
minute fungi develops. Small apothecia of various Disco-
mycetes usually appear in a week or two. A particularly
interesting genus is Ascobolus, in which the spores are some
shade of purple and the ripe asci project considerably be-
yond the general level of the paraphyses and unripe asci.
The phototropism of the asci in Ascobolus was first
described in 1890 by the great German mycologist, Zopf.
Ascobolus (Dasyobolus) immersus is an especially fine
species appearing very commonly on horse-dung. The
minute apothecium, less than 0-5 mm. in diameter, produces
about ten ripe asci at a time. These, however, are relatively
large and can easily be seen with a pocket lens. These
projecting asci are positively phototropic and bend so that
they point towards the light. Normally the spores from all
the ripe asci escape in a single puff, and for the week or so
of its active life the apothecium matures a fresh crop each
day. The last stage in development involves the pigmen-
tation of the walls of the ascospores, so that ripe asci are
clearly distinguishable not only by projecting beyond the
general level of the hymenium, but also by having deep
violet spores.