FOR many years the students of these plants have felt the need

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1 Reviexi\ 263 RnVIEW. BRITISH HEPATICS. FOR many years the students of these plants have felt the need of a work to give them further information and a better means of identification than could be obtained from the works of Cooke, Carrington, and Lett. This want was, to some extent, supplied by Pearson's " Hepaticse" (1) but the cost of this work was beyond the reach of many bryologists, and there was still plenty of room for a Manual at a less price and of a similar character to Dixon's handbook on the mosses (2). Hepaticologists can now rejoice in being able to possess such a work (3) and must feel deeply grateful to its author for the careful attention he must have devoted to the subject, in order to produce such an excellent handbook, remarkable not only for its lucid descriptions and notes, but also for its scientific accuracy, a combination not always obtained from systematists. The introduction gives a short and general account of the lifehistory of a liverwort, with some excellent notes on the collection and examination of specimens. The classification is based on Schiffner, many of the descriptions of the higher groups being taken directly from the works of this distinguished hepaticologist, but the author has not neglected the works of Campbell, Evans, Howe, Miiller, Spruce, Stephani and Cavers, the recent papers (4) of the latter being responsible for the elevation of the Sphserocarpales to ordinal rank. More species are given as British than in any previous work, this increase being partly due to recent discoveries and partly the result of segregation. The author can, however, hardly be considered to be a "splitter," neither can he be charged with being a " lumper," in media re sains, seems to be an excellent motto in this matter. Calypogeia, long known to British botanists under the name of Kantia, has seven species assigned to it, five others besides the distinct C. Trichomanis and C. arguta taking specific rank. The three larger species, Trichomanis, Necsiana and fissa {Kantia Sprcngelii, Pears.) are chiefly distinguished by the underleaves, which often vary in the same plant, and great difficulty is often experienced in deciding which of these names a specimen should bear, so that, at most, they can only be considered as " small species." C. sphagnicola, submersa, and suecica must be treated similarly, their specific distinctions from small forms of C. Trichonianis being of a more or less doubtful nature. A variety aquatica is given for C. Trichomanis whilst the equally definite aquatic form of C. fissa is not mentioned. Plagiochila has six species allotted to it, P. Stableri, "although only once collected and in small quantity," being judged as a distinct species. I have found occasional shoots of P. asplenioides var. humilis with an appearance almost exactly like that figured for P. Stableri, and as the original specimen was mixed with some of this variety, it may be a modification induced by edaphic conditions; P. exio-ua is reduced to a habitat-form of P. tridenticulata, P. killarniensis to a variety of P. spimilosa, and P. Owenii to a variety of P. punctata.

2 2 64 tieview. Lophocolea has a fifth species (L. alata) granted to it; this scarcely seems more than a variety of L. cuspidata with the wings of the perianth more highly developed. The confusion between the two species, bidentata and cuspidata has been dissolved, and L. fragans replaces the better-known name of L. spicata. Cephalozia has fourteen species, nine species formerly placed under this genus being allocated to Cephaloziella; C. curvifolia is placed in Nowellia, a genus named after the Yorkshire botanist Nowell; C trivialis and C. Curnowii are included in C. biflda, and C. yackii in C. myriantha, the smallness of these plants and the minuteness of some of the distinguishing characters causing differences of opinion of a quite legitimate nature as to the delimitation of these " small species." There are six British species of Fossombronia, these being distinguished chiefly by the number of lamellae or papillae on the spores ; in Riccia there are twelve species, R. natans, on account of its structure lieing placed in the genus Ricciocarpus. The Pallavicinia of most British authors is split up into two genera, Pallavicinia with one species, P. Lyellii, and Moerckia with three; Conocephalnm conicum represents our old friend Fegatella ; Pellia endivicefolia {calycina) appears in the unfamiliar guise of P. Eabbroniatta ; Nardia is repi'esented by four species respectively of Alicularia and Eucalyx, and Mylia has been displaced by Leptoscyphus. The old genus Lejeunia is separated into six genera, Lejeunea in its more restricted sense having six British species, Cololejeunea four, whilst Harpalejeunea ovata, Colurolejeunea calyptrifolia, Drepunolejeunea hamatifolia, and Mierolejeiuiea ulicina have their own generic names. Marchesinia claims priority to Phragmicoma by a single year and Gymnocolea is restored to the generic rank from which it had been temporarily displaced, the common species, G. inflata, having as a companion, G. acutiloba, of doubtful distinctness to G. inflata var. heterostipa, which has now found a resting-place from its tossings to-and-fro between Gymnocolea and Cephalozia. The more definite Jungermannia species are placed under Lophozia, containing twenty-six species, some of which are of doubtful specific value and can only be considered as " small species." L. turbinata and L. badensis are often difficult to distinguish from each other, the cell-size and amount of thickening (" trigones") at the cell-angles being variable in both plants. The three species, L. Floerkii, L. atteniiata and L. atlantica, though quite distinct in their extreme forms, have many intermediates which are difficult to refer to either, as the author subtly says "two allied species-vary in parallel lines so that the student may think that they have intergraded when such is not the case." The abundance of moisture causes atlantica to approach Floerkii; on the other hand, the di ier ground form of Floerkii has a very similar facies to that of atlantica. There is a drier ground form of L. ventricosa which bears a somewhat similar relationship to the type as L. atlantica does to L. Floerkii. Scapania with twenty-one species still retains the limits usually assigned to it, being practically the only genus, having more than five species, with unaltered boundary.

3 Reviexv. 265 In some cases (e.g., Aneuraand Cepbaloziella) great importance is attached to tbe distribution of the sexual organs, the unisexual or bisexual nature of the plant, being the character deciding its name. It may seem like heresy to the systematic hryologist to question tbe importance of this character, but a specific distinction based on such an unsatisfactory foundation is scarcely warrantable, especially when other species are not treated similarly. Tbe paroicous and monoicous conditions of Calypogeia Trichom/inis are not considered specifically distinct, but a similar sexual distribution in Cephaloziella causes a segregation into two distinct species, other differences being of minor importance in the naming of a doubtful plant. The same uncertainty of specific distinction is shown in Aneura latifrons and A. incurvata; the former is monoicous, usually broader, more branched and plano-convex in section, whilst tbe latter is dioicous and concavo-convex in section. The characters separating these two plants are very variable, dioicous plants sometimes having the form and section of A. latifrons, in fact, tbe shape of tbe crosssection of tbe tballus may vary in the same specimen, in which case the sexual distribution seems to be the only distinguishing character between the two species. Cephalozia Lammersiana was regarded by Spruce as a larger and dioicous form of C. bicuspidata, whilst Macvicar considers it to be only "pseudo-dioicous," and as "a 'small species' which is probably not always separable from C. bicuspidata." In the nomenclature of mosses (2) the same unsatisfactory distinction occurs, Bryum bimum, being synoicous, is separated from B.pseudotriquetrum wbich is dioicous, the autoicous B. pallescens from tbe synoicous B. affine, the distribution of the gametangia being tbe only constant separating feature. In B. capiuare the synoicous state is simply given as a variety of the dioicous type, and B. inclinatnni and B. provinciale may be autoicous or synoicous, sometimes botb arrangements of the gametangia occuring on the same plant. There are seven species of Aneura given ; those most recently segregated, A. incurvata and A. major, are probably much commoner than indicated, especially if the simple and concavo-convex character of the tballus be taken as the deciding factors of tbe former. The crassior form of A. pinguis found on sand dunes seems to be as worthy of a varietal name as many others which have been accorded that doubtful dignity. The use of a varietal name is, as the author says, " largely a matter of personal opinion," and probably no two hepaticologists could be found to agree in all cases, but tbe values of some of the varieties given in the Handbook seem unequal to me. Of doubtful value may be mentioned such varieties as tbe following, Riccia glauca vars. major, minor, siibinermis; R. bifurca var. subinermis ; R. Warnstorfii var. subinermis; Scapania gracilis var. minor; Chandonanthus setiformis var. alpimts; Lophozia Floerkii var. Naumanniana ; Alicularia scalaris var. procerior ; and Cephalozia media var. laxa. In most cases these are growth-forms due to habitat, as such a good ecologist as Macvicar no doubt recognises. The erect, truly aquatic form of Pellia Fabbroniana is given as var. lorea] the similar habitat-form of Marchantia polymorpha is var. aquatica, the more xeropbytic and alpine form of tbe latter being distinguished as var. alpina.

4 2 66 Review. Alicularia Geoscyphus has a form of shady or moist ground which is the var. suberecta {=jfungermannia silverettce); in intermediate habitats all stages between the type and the variety can be found and " it cannot always be distinguished from the typical plant" (3). No varieties are given for Gymnocolea inflata, but from the way in which varietal names have been bestowed, some of its forms have a right to be classed as varieties, since a great difference exists between the two extremes, the form compacta of dry situations, and the form natans which occurs as free-swimming tufts in pools. Lepidozia pinnata has a var. minor, whilst the equally distinct laxer state is merely referred to as form laxa, the lax form of Lophozia Schultzii being styled var. laxa. The confusion between the greenish, less-toothed forms of Scapania dentata (more familiar as is. purpiirascens) and the purplish, more or less toothed forms of vs. 7»»/!t/rt^rt is avoided by placing the "intermediates" in the var. ambigua of the former, a procedure which is certainly warranted by my experience of the plants, though it leaves some room for doubt as to the specific distinction between nndulata and dentata. The larger-celled form of CJiiloscyphus polyantlius, which has been so often mistaken for C. pallescens is called var. fragilis. These criticisms are not in any sense, to be taken as pointing out defects in the work, but as indicating the different points of view that may be considered by other hepaticologists in tising specific and varietal names. Mr. Macvicar is too good an ecologist to be dictatorial in such matters, and many of the names used have doubtless been adopted after some hesitation, and in some cases he may have sunk his own personal opinion below that of other writers. It is extremely interesting to note, that owing to the aid and stimulus which thi.s work has given to British students since its publication, seven species and one vai-iety have been added to our Hepatic flora, and that most of these were mentioned in the attractive foot-notes as likely to occur in our isles. Marsupella apiculata, Lophozia longiflora and Diplophyllum gymnostophilum have been found in tbe Scottish Highlands, Lophozia confertifolia in N. Ireland and Sussex, CepJialoziella Douini in Kent, C. pidchella in Nortbants and Yorkshire, and Riccia commutata and its variety acrotricha in Sussex. This is a striking testimony to the value of the work, which gives not only descriptive notes and excellent keys of the genera and species, but is also well-indexed and ably illustrated by W. G. Jameson, to whom, as well as to the author, the British students of these plants feel a deep debt of gratitude. W. WATSON. (1). Pearson, W. H. "The Hepaticse of the British Isles." London, (2). Dixon, H. N. " The Student's Handbook of British Mosses." Ed. 2, London, (3). Macvicar, S. M. "The Student's Handbook of British Hepatics." London, (4). Cavers, F. " The Inter relationships of the Bryophyta." NEW PHYTOLOQIST, ; also published as "NEW PHYTOLOGIST Reprint No 4," London (Wesley), 191L

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