108 
THE DUAL-LICHEN HYPOTHE8IS. 
Any one who has examined the thallus of such a Lichen as 
Peltigera canina , and compared it with any known species of the 
Discomycetes, must come to the conclusion that amongst them 
there is no such structure to be found as that which prevails in the 
Lichen thallus, altogether irrespective of gonidia. 
It is sometimes useful and instructive on doubtful points to con- 
sult the instincts of the lower animals, and this course may be 
adopted with advantage in the present instance. Amongst Coleop- 
tera, there is an entire family called the Mycetophagidce , many of 
which live upon Fungi, and yet do not attack Lichens. There are 
also some of the Bostrichidce, and some species of Anobium very 
fond of Fungi, but they do not attack Lichens. The insects which 
destroy Lichens are few in number, and quite different in their 
relationships from those which prey on Fungi. 
There is also amongst the Diptera a family called Mycetophilidce , 
with like propensities, as evidenced by the genera Mycetophila , 
Boletina , Mycetobice, Bolitnphila , and yet there are none so equally 
destructive or parasitic on Lichens. 
These insects must have come to a sounder conclusion than 
some men, that Lichens are not Fungi, with the addition of an 
innocuous green Alga. Surely if they had the same grateful 
food to offer, these insects would patronise the Lichens ; but as 
they attack all kinds of Fungi, and do not attack Lichens, in- 
sects certainly have not yet become converts to the Schwende- 
nerian hypothesis. 
In concluding these comparisons, the only inference which ap- 
pears feasible is, that all these differences are so many reasons 
against the identity of Fungi with Lichens. There must be a most 
essential difference between them, beyond the gonidia, for the 
gonidia are not sufficient causes to produce all these divergencies. 
It is quite erroneous to state, as some have done, that the 
gonidia constitute the only difference between Lichens and Fungi, 
whereas the presence of gonidia is only one out of many differences 
which exist between them. 
(To be continued.) 
LICHEN FLORA. 
We are happy in being able to announce that Rev. W. A. 
Leighton has nearly completed the printing of the third edition of 
his “ Lichen-Flora of Great Britain, Ireland, and the Channel 
Islands,” which it is expected will be ready for issue early in 
March. This new edition is rendered necessary by the marvellous 
discoveries of Mr. Larbalestier in the West of Ireland, those of 
Mr. Crombie, Dr. Stirton, and others in the North of Scotland, and 
his own researches in North and South Wales, whereby the Lichen- 
Flora of the former editions, amounting to 1,156, has been raised 
now to 1,706, thus rendering our Lichens, in number, rarity and 
novelty, quite equal to those of any country in Europe. 
