66 
REVIEWS. 
and also entering into the internal anatomy of the plants—in fact, a careful 
resume of all that is known on the subject. Next, a chapter on the 
economic uses of lichens, which are stated to be three—food, dyes, and, 
lastly, as nature’s pioneer, to prepare the barren rock and desert island for 
the habitation of higher plants, and, finally, of animals. To this last theory 
we must express our dissent; for, though it is a pretty one and prettily 
handled in the book, yet we fear it must be abandoned in our present state 
of knowledge; for, even granting, which cannot be denied, that lichens do 
erode the rocks to which they are attached, and that they are (though this 
we doubt as an universal rule) always the first plants to take possession of 
the newborn land, yet, taking into account their slow growth and equally 
slow decay, and the minute quantity of organic matter that thereby arises, 
it is impossible to conceive that they can play so important a part as here 
assigned them; and, if the author had ever an opportunity of examining 
those barren rocks, in tropical regions, where lichens most love to grow, he 
would have found physical causes sufficient to account for the formation of 
soil, in the wearing effect of the sun’s heat; and, though it may sound 
strange to our northern ears, we suspect also of the heavy night dews 
playing, amidst the heated tropical rocks, a part analagous to that which frost 
and rain play amongst the cliffs of northern and southern lands. Into the 
subject of the dyes derivable from lichens the author enters very 
fully, giving concise and simple methods for testing the value of 
the various species; and the importance of this family, in a com¬ 
mercial point of view, may be judged of by the fact that £1,000 a ton 
has been paid for Orchil. Next, an interesting chapter on the geo¬ 
graphic distribution of lichens, from which it appears that many of them 
are cosmopolitan, and also the most extreme representative of vegetable 
existence, whether we arrange plants latitudinally or altitudinally. That 
pretty little species, Lecidea geographica, common on our Irish quartz 
hills, “also occurs in the arctic and antarctic regions, and is the last form 
of vegetable life which has been met with by travellers in the greatest ele¬ 
vations hitherto reached on the Andes and Himalaya.” The important 
influences exercised by habitat over the forms of these plants is also noticed, 
as well as the geologic distribution of many species. We must pass un¬ 
noticed “ On the collection and preservation of Lichens,” and come to an 
important chapter on classification. The author, while, in our judgment, 
showing his good sense by adopting “a natural instead of an artificial 
classification—a classification founded on natural affinities and structural 
analogies, rather than one based on the reproductive -or vegetative systems 
