THE STUDENT S HANDBOOK OF BRITISH MOSSES. 515 primary division into Acrocarpi and Pleurocarpi, to which they have been accustomed, is abandoned, they will yet find the Pleurocarpi all together at the end of the list. They must, however, look for the GrimmiacecB earlier in the list, and no longer in the neighbour- hood of the Orthotrichacem. The cleistocarpous forms are distributed and placed in those orders to which they show vegetative affinity. Modern researches into the peristome have led to the interesting speculation that the differentiation of most types of sporogonium must have been completed before the elaboration of the oophyte (or vegetative part) into stem and leaf began. Thus the primeval type of Moss, consisting principally of protonema and fruit, is indicated to us by that curious survival, Buxhaumia {Handbook, p. 47). Against the synonymy of the species it must be urged that it is open to objection on the score of excessive brevity in being limited to the original name of the plant, together with the subsequent names adopted by Schimper and Braithwaite — and by Lindberg in the case of the Pleurocarpi, on the presumption that Braithwaite will extend the Lindbergian notation to this group. This brief synonymy may perhaps satisfy the beginner. But Mr. Dixon should have borne in mind that his new Handbook is the only complete and adequate modern treatment of our Mosses, and as such will replace Wilson's Bryologia Britannica (1855), our old standard work with its now archaic nomenclature. Hence he should have arranged for a ready reference from the one book to the other. For, as it is, the inexperienced student will find no direct connecting link between the Oligotrichum incurvum and Cylindrothecium concinnum of the newer book and the 0. hercynicum and C, Montagnei of the older. Again, the species of Webera are only to be collated with the corresponding species of Bryum in the ** Bryologia" indirectly through the Pohlia synonyms which are common to both books. Similarly, in cases of Ceratodon cylindricus, Bryum demissum, Iso- thecium alopecurum, Pterogonium filiforme, Leskea riifescens of the
- ' Bryologia," which have to be traced through synonyms to their
equivalents in the Handbook. The few additions necessary for removing such defects would have increased Mr. Dixon's text to an inappreciable extent, and would have been of great assistance to the old-fashioned Moss-student. -A.i«l u-. The distribution of the species Mr. Dixon hmheeki constrained to limit to broad generalized statements for two reasons — lack of materials for drawing out a complete list of localities, and lack of space to print it. But he gives the localities of the rarer species. One new species — FonUnalis Bixoni Cardot — makes its debut in the Handbook, and one new subspecies — F. dolosa Cardot; and there are six new varieties, to four of which Mr. Dixon is godfather. Attention may be called to the almost simultaneous publication of descriptions of Fontinalis Dixoni and F, dolosa by Cardot himself in the Revue Bryologique (1896, pp. 70 & 68). Ther« F. rfoZosa ranks ias a species. i — -sij^ji- ^ v-v^, ,— , ,iy:n)j.y; ■■^-■ -ij Some changifee ifjgenferic nomenclature call^te'*i^mairk^-the substitution of Weisia in an extended sense and Tnchostomum for MoUiayOf Porotrichum for Thamnium, and of Pleuropus for Homalo-
