AS the author states in the preface, “The present Hand-book is planned upon the same lines as Hooker and Baker's ‘Synopsis Filicum,’ and the two, taken in connection, cover the whole series of the Vascular Cryptogamia.” The total number of species described in the “Hand-book” is 566, and as we may now place the number of known ferns at about 3000, the fern-allies may be taken to represent about one-seventh of the recent Vascular Cryptogams. The fern-allies include only eleven genera, and about four-fifths of the species belong to the two genera Selaginella (335 species) and Lycopodium (94 species). The eleven genera are placed by Mr. Baker in four “natural orders,” while the Filices form a fifth: three of these, Filices, Equisetaceae, and Lycopodiaceae, being isosporous; and two, Selaginellaceae and Rhizocarpeae, being heterosporous. In this way the relationship of the Rhizocarpeae to the ferns is quite lost sight of; the Selaginellas and Lycopods are separated more widely than is desirable, and no place is left for the fossil heterosporous Equisetinae. The arrangement adopted by Mr. Baker is very good for herbarium work; but for classificatory purposes it ignores certain palaeontological facts which we cannot at the present day afford to overlook. Mr. Baker, however, does not deal with the fossil types, and now that we have such a complete account of the recent forms, let us hope that before long we may have as complete a synopsis of the fossil forms; a work which would be of the greatest interest and importance. Hand-book of the Fern-Allies: A Synopsis of the Genera and Species of the Natural Orders Equisetaceae, Lycopodiaceae, Selaginellaceae, Rhizocarpeae. By J. G. Baker, First-Assistant in the Herbarium of the Royal Gardens, Kew. (London: George Bell and Sons, York Street, Covent Garden, 1887.)