to be, and also that he had made a study of Ferns, and accepted my father's limitations of their genera and species. I therefore requested that gentleman to undertake the work, which to my great satisfaction he has done. The _Synopsis Filicum_ contains 75 genera, and about 2252 species, inclusive of Osmundaceae, Schizaeaceae, Marattiaceae, and Ophioglossaceae, which are not included in the _Species Filicum_." This work summarised the Pteridological results of Sir William Hooker's life. The total number of plates of ferns published by him is about 1210, embracing 1267 species, of which about 250 appeared under the joint authorship of Dr Greville and himself. These figures are in themselves sufficient evidence of the extent of his Pteridographic work. It has been noted that the number of genera in the _Genera Filicum_ was 135, maintained approximately according to the limitations of Presl in his _Tentamen Pteridographiae_: allowance has, however, to be made for 23 genera of Parkeriaceae, Schizaeaceae, Osmundaceae, Marattiaceae, Ophioglossaceae, and Lycopodiaceae, which were omitted in the _Tentamen_. But in the _Synopsis Filicum_ there were only 75. It is true that the three genera of Lycopodiaceae were excluded also from the _Synopsis_, but still there is the wide discrepancy between 132 of Presl's genera as against 75 in Hooker's _Synopsis_. This at once indicates a salient feature of his method. He merged a large number of genera, ranking many of the smaller ones as sub-genera under the more comprehensive headings. Doubtless the reasons for this were various. One was his mistrust of anatomical data, which it must be confessed Presl put too much in the fore-front. The very first sentence of the _Tentamen_ runs thus "Vasa plantarum principale signum esse ex eo patet, quod exinde primaria divisio omnium plantarum exstitit." But occasionally Sir William explained his reason in a specific case. Thus in the question of Kunze's sub-genus _Plagiogyria_ of the genus _Lomaria_, which Mettenius had raised to the dignity of a distinct genus, he explained his reasons for merging it into the genus Lomaria. Mettenius had laid stress upon various characters, but especially on the _oblique annulus_ as distinctive. On this Hooker remarks "even should the capsules in all the species referred to _Plagiogyria_ prove to be helicogyrate, yet the habit and sori are so entirely in accordance with true _Lomaria_ that, unless the student has the opportunity of examining very perfect specimens, or unless he examines the structure of the annulus of the very minute capsules under the high power of the microscope, the genus cannot be identified. Kunze only proposed to form a group or section under the name of _Plagiogyria_, but even that would be found inconvenient to retain in a work whose main object is to assist the tyro in the verification of genera and species: and natural habit is often a safer guide than minute