484 
NATURE 
[ Océ. 19, 1871 



that such works as the present are calculated not to 
create Biologists, but to perpetuate a race of mere 
collectors and labellers—men whose highest aim is to 
gather “new” or “‘rare” species ; who spend their holidays 
in accumulating sfeczmens, sending those that are un- 
familiar across the Channel for identification or naming. 
One of the results of the latter procedure is that the 
present work contains no less than 200 British species or 
varieties bearing Nylander’s name as the author of their 
first description ! 
While, however, meagre attention has been thus be- 
stowed upon the secondary reproductive organs, undue 
prominence is given to the action of potash and lime on 
the thallus and apothecia, and the reaction of iodine with 
the hymenial gelatine ; phenomena that are so uncertain 
and inconstant that they vary even in the same individual 
under different circumstances. We would not exclude 
chemical or ay natural characters from the definition of 
species ; but the present work seems to us to furnish ample 
illustration of the danger of making use of secondary, 
trivial, inconstant characters as a basis for classification 
(e.g. the genus Cladonia.) 
The localities of growth are satisfactory so far as they 
go; but they are utterly inadequate as representing the 
distribution of species in either of the three kingdoms, In 
order to specify, with at all adequate fulness, the diversity 
of locality occupied in England, Scotland, and Ireland 
respectively by the species enumerated, Mr. Leighton 
must have examined for himself the contents of all the 
Lichen-Herbaria in these kingdoms ; and, though the said 
herbaria are neither numerous nor large, compared with 
those of flowering plants, such a labour is obviously im- 
possible for any ove man of average leisure and oppor- 
tunities. 
There is no Tabular Summary showing the numerical 
richness of the British Lichen-Flora ; an omission, it may 
be, of minor importance, but still of importance, inasmuch 
as it is always interesting to “take stock” occasionally of 
the rate of progress of the additions that are being made 
to a national Sub-Flora. Basing our calculations on the 
data supplied by the present work, we find a total of 73 
genera and no less than 781 species ; whereas only last 
year in his enumeration, Crombie (p. 124), gave the whole 
number of British Lichens then known as 658, the dif- 
ference apparently representing, or consisting of, so-called 
new species. Of the host of these ~ew species added of 
late years to our Lichen-Flora, perhaps not above one- 
fifth will survive in that “ struggle for existence,” to which 
they will sooner or later have to submit at the hands of 
the philasophic botanist. A large proportion will doubt- 
less be found to consist of mere forms of common, pro- 
tean, widely distributed species—forms that neither require 
nor deserve separate nomenclature and rank. 
We have not exhausted the list of blemishes in the 
book before us. But to notice @// the errors in matters of 
detail ; all those points on which other lichenologists are 
likely to take grave exception to his views ; all the faults 
in typography or otherwise, would extend and expand this 
review into a Treatise on the Classification of Lichens ; 
for it would necessarily deal with certain features of 
that Nylanderian system, which Mr. Leighton follows in 
his present work, 
With all the aids the author gives the student, it will, 

we fear, be impossible for the latter to identify the majority 
of the less common and familiar species without reference 
to authentic specimens named by Mr. Leighton himself. 
The work is so elaborate and complex, the principles and 
practice of classification adopted in it areso puzzling, that we 
candidly confess our own general impression to be one of 
increasing bewilderment, and of growing indisposition to 
attempt the identification or nomenclature of Lichens at 
all! We hesitate not to avow our own preference for 
studies on the Biology of the common economical species, 
such as those which af present are called Cladonia ran- 
giferina, Usnea tarbata, Ramalina calicaris, Parmelia 
saxatilis, Roccella tinctoria, or Lecanora tartarea. 
On the whole, however, the “ Lichen-Flora of Great 
Britain” is a work that should find a place in every public 
botanical library in the three kingdoms, as well as in the 
private libraries of all students of the extremely puzzling 
cryptogamic family of which it treats. 
W. LAUDER LINDSAY 


OUR BOOK SHELF 
A Complete Course of Problems in Practical and Plane 
Geometry, adapted for the Use of Students preparing for 
the Examinations, &c. By John William Palliser, 
Second Master and Lecturer of the Leeds School of 
Art and Science. (London: Simpkin and Marshall.) 
A NEw class-book on Practical Geometry commends itself 
to our attention. Mr. John Palliser, of the Leeds School 
of Art and Science, has produced one of those educational 
works which a demand created by Government examina- 
tions has recently brought to our aid. Reserving our 
opinion as to the final tendency of an epidemic for what 
are called practical results, we must, in justice, say that 
this class-book of Mr. Palliser’s is the very thing for 
cheapness, conciseness, comprehensiveness, to rapidly 
possess the student with a ready-handed ability to answer 
all demands of the examiner. The work is not encum- 
bered with demonstration, for this, in view of the proposed 
end, would be out of place ; it is a laboratory of experi- 
mental formule. We have a recipe for constructing all 
conceivable polygons within the compass of a single 
circle, for drawing lines to invisible points, and for trisecting 
the most obdurate angles by the magic of a slip of paper. 
Faith is all that is demanded of the student, faith in the 
formule before him, and industry to get them by heart. Not 
troubled with the Why, he has only toremember the How ; 
but he must be careful, exact, and neat-handed; and this, 
if not mental training, is next of kin toit. The arrange- 
ment of the book is generally good, the style concise in the 
extreme, the letter-press wonderful at the price, and the 
diagrams, with their faint, dark, or dotted lines, are highly 
effective and intelligible, not less so from the fact of the 
lettering being (what we very seldom find it) correct. 
To examine in detail the 220 problems of Mr, Palli- 
ser’s book is more than we can just now undertake ; but 
so far as we have dipt into them there is little to complain 
of, considering that the work is merely practical. The style, 
we have said, is concise ; but (if we might venture a criti- 
cism on a point where most geometers are more guilty 
than Mr. Palliser) it would lose nothing in intelligibility if 
the nominative case were less frequently preceded by a 
multitude of perplexing conditions which really have tq 
be neglected by the learner till the sajd nominative is 
reached, and then returned te lastly in that natural order 
of thought which geometers have a fancy for inverting. 
Whilst taking these minor exceptions, we must not omit to 
call the author’s serious attention to Problem 13, which, 
whether we consult the diagram or the letter-press, is 
wholly fallacious. Such a construction will not effect the 
