NATURE 
THURSDAY, AUGUST 21, 1902: 
A MONOGRAPH OF THE BRITISH 
LIVERWORTS. 
The Hepaticae of the British Isles, being Figures and 
Descriptions of all Known British Species. By 
William Henry Pearson. Vol. i. text, vol ii. plates. 
Pp. vi + 520, and vil + plates 218. (London: Lovell 
Reeve and Co., Ltd., 1902.) Price 7/. ros. net. 
TRUSTWORTHY work on the British Hepaticze 
has long been needed by those who are interested 
in this somewhat difficult group of plants. Since the 
appearance of Sir W. J. Hooker’s “‘British Junger- 
manniz” in 1816, we have had no treatise on our native 
species that can be regarded as either up-to-date or as 
of much use to the student. A beginning was made 
some years ago by Dr. Carrington in cooperation with 
the author of the volumes before us, but, unfortunately, 
the attempt was not destined to meet with success, and 
the enterprise was abandoned at an early stage of its 
publication. 
So many new forms have been added to the British 
flora since Hooker’s time, partly as the result of revisions 
of older species and genera and partly owing to the 
discovery of new ones, that the whole subject has come 
to present a very different aspect from that which it wore 
ninety years ago. The vast majority of hepatics were 
then included in the single genus Jungermannia, whereas 
only comparatively few species are now retained in it. 
A more extensive study has gradually rendered it 
possible to segregate the species into smaller and more 
natural groups, such as are familiar to those who have 
been accustomed to use the well-known “ Synopsis 
Hepaticarum” of Gottsche, Lindenburg, and Nees vy. 
Esenbeck. 
It is pleasing to remember that our own countryman 
Spruce, who added so much to our knowledge of liver- 
worts, was one of the foremost to discriminate between, 
and give expression to, the affinities existing between 
the species of the larger and more complex genera. He 
was thus able to break up these unwieldy collocations 
of species into smaller and more manageable subgenera. 
Mr. Pearson, in the fine work before us, has adhered 
to the general arrangement of Spruce as laid down 
by him in his “ Hepaticae Amazonice” and elsewhere, 
which has, with more or less modification, served as the 
basis for most of the modern forms of classification. 
The first volume is devoted to the text, and opens with 
an introductory chapter in which organography and 
other preliminary matters are very briefly dealt with. It 
is in connection with this chapter that we would express 
regret that Mr. Pearson should have allowed to slip by 
the opportunity of attempting some reform in the esoteric 
terminology that has grown up in association with this 
group of plants. Many terms possessing a perfectly 
well-known meaning in connection with the rest of the 
vegetable kingdom are, in the systematic literature of 
Hepatice, habitually distorted so as to imply something 
totally different from what they mean elsewhere. Thus 
the so-called stipules are not in the least degree com- 
parable with stipules as generally understood, and the 
NO. 1712, VOL. 66] 
385 | 
word ought to be altogether dropped in favour of 
amphigastria, a neutral term that may well be retained 
to designate the ventral leaves of these, usually dorsi- 
ventral, plants. The radially constructed species prove 
clearly enough that the amphigastria have nothing to do 
with true-stipules, but are merely special leaves which 
owe their particular (often reduced) form to the dorsi- 
ventral habit of the stems. To continue to apply the 
older and misleading term of stipules to these structures 
is clearly an unjustified anachronism. Similarly, the 
expressions ‘‘Postical” and ‘Antical” might with 
advantage be replaced by the words Dorsal and Ventral, 
as universally used elsewhere. And once more, why 
continue to speak of “ Pistillidia” instead of Archegonia, 
the word invariably employed in modern botanical 
works to designate these structures? Of course, Mr. 
Pearson is not to be held responsible for the introduction 
of these terms ; they are of hoary, and we had hoped of 
senile, antiquity. And though he has probably retained 
them purposely, we could have wished that he had 
otherwise decided. 
As regards the rest of the work, there is much deserving 
of praise. The descriptions of the species are clear and full, 
and the shorter notes that accompany inany of them are 
interesting and often of critical value. Especially is this 
the case with species likely to be easily confounded. The 
special diagnostic characters are then discussed and em- 
phasised, as, for example, in the two common species of 
Pellia, P. calycina and P. epiphylla. Curiously enough, 
however, no reference is made to the anatomical differ- 
ences, pointed out by Leitgeb, between the cells of the 
thallus in these two plants. The geographical distribution 
of each species is mentioned, and frequently the actual 
localities also. Naturally these are not exhaustive, and 
those especially who have collected the plants in the more 
southern parts of England will be able readily to supple- 
ment them. Some species that are described as rather 
rare, e.g. Reboulia hemispherica, would probably not be 
so regarded by many people. A glossary, table of litera- 
ture and a good index complete the volume. A chapter 
on the interesting biological features in which the liver- 
worts are so exceptionally rich would have been a wel- 
come addition to the book. There is hardly another 
family of plants that displays so manifold a variety of 
form or such a remarkable series of structural modifica- 
tion in relation to the environment as does that of the 
hepatics, and these fascinating adaptations deserve far 
more attention than they commonly receive. 
The second volume is devoted to the figures, and it con- 
tains no fewer than 228 plates. These form a splendid 
adjunct to the text, and will prove of material service in the 
proper identification of the various species. The plates are 
in nearly all cases excellent, and each generally includes a 
life-size representation of the species, as well as drawings, 
on a large scale, of dissections, fructifications, &c. The 
cellular structure of the leaves is also depicted, and this 
will often be found of much value in deciding between 
doubtful cases. In the genus Fossombronia the spores 
| are carefully drawn, as furnishing perhaps the most 
easily recognised characters by which the species of this 
somewhat difficult genus can be identified. 
Although we have freely criticised certain features 
in the book wherein our own judgment happens not 
iS) 
