16 THE ESSEX NATURALIST
no answer. The fungus is presumably the imperfect stage of an
Ascomycete, but no ascus stage is known. We guess that infection
usually takes place by wind-blown spores, entering through
broken off twigs and branches in the crown of the tree (die-back of
upper branches often precedes infection near ground level).
Whether the Lathrydid beetle, Enicmus brevicornis Mann., which
has often been found eating the spores where the roof stroma per-
sists on old lesions, plays any part in dispersal of the fungus we do
not know. The connection between stained wood and sporing
lesions requires elucidation. Is the stain in the wood a diffusable
substance produced where the fungus invades bark and cambium?
Or is it a sign that the wood itself is invaded by the fungus?
The fungus appears to be a recent introduction to this country
and its geographical distribution raises some interesting problems.
How did this fungus, presumably a harmless saprophyte on
North American maples, reach this country? Is its present con-
centration in the London area due to the time since its arrival
being too short for it to have spread more widely? Will it prove
lethal in other areas? Or are conditions in the London area par-
ticularly suitable for invasion of living trees by the fungus and for
spread from one tree to another? What measures are necessary to
prevent the infection of healthy trees, and to prevent spread into
new areas?
The future of the sycamore in England is equally problematical.
Will the disease decline in importance, or perhaps remain re-
stricted to urban areas? Will it become chronic like the elm
disease? Or will it wipe out the sycamore in this country as
thoroughly as Endothia parasitica destroyed the chestnuts in the
Eastern United States?