75 
and the causes affecting its recent diminution. 
Sucli causes as those now mentioned, tending to the 
diminution of the lichen-flora of the Forest, were probably 
more or less at work in the days of Forster; but there can 
be no question that of recent years they have been much 
more actively and extensively in operation. It will therefore 
be very interesting to the lichenist of the future—some fifty 
or a hundred years hence—to compare the above list of 
lichens with those that the Forest may then present. Some 
species belonging to the higher genera extant in Forster’s 
time, and some also belonging to the lower genera, noted in 
the catalogue as extinct, can never again be expected to 
occur, since they are not elsewhere to be found within such 
a measurable distance as that their spores could be readily 
disseminated in the Forest. But now that the Forest is 
strictly preserved and left to the operations of natural laws, 
there is every reason to believe that many species and 
varieties now germinating and slowly growing upon their 
different substrata may eventually be found developed into 
perfect thalli or fertile plants. This, however, must be the 
work of time : for though readily germinating, the subsequent 
evolution of lichens is in most cases a very protracted process, 
resulting from their peculiar twofold manner of life—lethargic 
in dry, and active only in wet, weather. 
