Page:Journal of botany, British and foreign, Volume 34 (1896).djvu/550

 514 THE student's handbook of BRITISH MOSSES. This was the Illustrated Guide mentioned above. So useful and trustworthy was it found to be, and so practical in its working — with its unique feature that it rendered possible the identification of barren mosses — that it was greatly in demand ; and the whole edition was soon exhausted. Once more the scene changes, and we have before us the subject of the present notice. Mr. Jameson's keys and plates no longer stand alone, but, remodelled and redrawn to suit the context, are incorporated in a new handbook written by Mr. Dixon. , Mr. Dixon's work — it should be said at once — is in no sense a mere compilation, but is a genuine description of the plants from his personal knowledge of them in both the living and the dried state ; and the descriptions are both careful and harmonious. A welcome feature, which is novel to British Moss literature, but has been employed by some foreign writers, is the italicizing of the most distinctive characters of the genera and species — a thoughtful provision which will save us much time in the identification of specimens. To the generic and specific descriptions are appended notes which will prove eminently helpful to the student in the discrimination of plants that are closely allied or deceptively alike. At the same time these notes may, in so far as they are critical, elicit the approval or disapproval of the advanced worker, according to the views he may entertain of the values of species. And this will apply to the subspecies — another innovation which Mr. Dixon has introduced in order the better to express the conclusions at which he has arrived with regard to the claims the plants possess to qualify as species or less than species. He always clearly states his reasons for changing the rank of a plant, and as a genuine worker he has as much right to put forward his own opinion as anyone else has to maintain an opposite opinion. Moreover, the subspecies are as fully described (and figured by Mr. Jameson) as the species, and merely differ in being indicated by an asterisk instead of a number ; hence the introduction of subspecies will in no way diminish the utility of the book to the student for whom it is principally intended, ''the primary object of this work being," says Mr. Dixon in his Introduction, "to simplify the determination of our British Mosses for the student, and to make it available, as ifpaf as possible, for a beginner." n, >; The system of classification is that of the second edition of Schimper's Synopsis (1876), modified, however, in the light of Philibert's researches into the structure and development of the peristome. The Mosses are divided into three subclasses — Sphog- 7iales, AndrecEales, and Bryales, the latter being again divided into two groups — Nernatodontece (including three orders — Tetraphidacea, Polytrichacew, and Buxbaumiacece) and Arthrodontea. The Arthro- dontecB fall into two subgroups, of which the one — Aplolejndea — contains five orders (Dieranacea, Fissidentacea, Grimmiaceay Tortu- lacea, Encalyptacecp), and the other — DijololepidecB — is further divided into two sections, the first comprising the rest of the acrocarpous orders, and the second all the pleurocarpous. This arrangement is somewhi^trBQ^^^to British folk ; but, though they will see that the