270 REVIEWS. 
ancient botanists. Hymenodecton, Chiographa, Aulacographa, 
Lecanactis, are also founded on species of the same genus Ope- 
grapha. Platygramma isa new genus, for which we do not per- 
ceive any other authority than that of the author of this Mono- 
graph; the species, or one of them at least, appear to be equally 
original (new). We hope that all interested in British Licheno- 
graphy will purchase this Brochure, and we hesitate not to say 
that with the aid of the very characteristic diagrams of the spo- 
ridia, asci, lirelle, etc., together with the detailed verbal descrip- 
tions, they will have no difficulty in identifying the species of this 
tribe. For ourselves, and for the botanists of Great Britain gene- 
rally, we cheerfully acknowledge our obligations to the author of 
this very learned and explicit Monograph, and we congratulate 
him on the successful issue of his meritorious labours. 
With all possible deference to the majority of our readers, who, 
we are convinced from personal knowledge, are as well or better 
acquainted with Lichens than ourselves, we would write some- 
thing for the edification of such as do not know what Lichen 
means. For the information of such tyros, it may be stated, in 
the first place, that these plants (Lichens) abound everywhere 
except in the water and in the atmosphere; and it is probable 
that their sporidia (reproductive matter) may exist im both these 
elements. They grow on all uncultivated parts of the ground, 
whether it be moist or dry; rocks, stones, bricks, tiles, slate, 
‘old thatch, are more or less covered by them; except stones in 
cultivated places, and on roads, streets, etc., Lichens never grow 
on such: they abound on trees, especially where the atmosphere 
is moist; also on old palings of parks, on old barns, especially 
when erected of boards. They appear to be the most permanent 
forms of vegetation, surpassing in longevity the Oak, the Yew, 
and even the Baobab or Monkey-bread tree of Senegal, which 
Adanson conjectures is older than our first parents, for it has 
survived all the generations of men that have lived since the 
Creation. The Lichens appear to be as old as the rocks on which 
they grow. We leave to the geologists the determination of 
the period when these, the more solid portions of the earth’s 
crust, had their beginning. We do not mean that Lichens are 
as old as every rock on which they are now seen; many rocks 
did not emerge from the water or from the land till some time 
after their creation; but we do mean that rocks above ground 
