6 
DEVELOPMENT 
the past ten years, and it is noticeable that certain species 
— e.g ., Boletus piperatus and Hygrophorus calyptvceformis — 
appear in three-year cycles, and are not seen in the inter¬ 
vening years. 
Whether living in wood or in the earth, the mycelium of 
some species persists for a very long time. Year after year 
the sporophores of Fistulina hepatica will appear from a 
crack in an oak trunk ; Xylavia hypoxylon persists for many 
years on the same stump, and many other instances could 
be given. There are also some curious records of fungi 
appearing suddenly in exactly the same spot after a long 
interval. One of the most remarkable that I am aware of 
is given by Fries (“ Epicrisis,” p. 223). He remarks that 
Hypholoma storea (a rare species) was found on a decaying 
part of a living beech trunk in 1815, and that it appeared 
from the same crack again in 1833. 
Cooke and Berkeley observed, concerning Cmterellus covnu- 
copioides , that “ some ten years ago it appeared in one wood 
at a certain spot by hundreds, whereas during the past three 
or four years we have failed to find a single species.” They 
also remark: “ It is certain that plants found by Dickson, 
Bolton, and Sowerby have not been detected since, whilst it 
is not improbable that species common with us may be very 
rare fifty years hence.” As with the higher plants, so is it 
with fungi—the appearances and disappearances of many 
are in all probability largely affected by alterations in their 
environment. Clear away the undergrowth and thin out 
the trees in a wood that has been carefully and systematically 
observed during many successive years as regards its flora, 
and what strange results accrue! To quote an instance 
that has recently come under my observation: A common 
near Haslemere was in one part thickly covered with oak 
and holly, with a sprinkling of beech and birch. Very few 
wild flowers occurred, and these only at the edge of the 
thicket. The fungus flora was meagre and without interest, 
