meaning from that expressed by the same term when the work was commenced. The annexation of Texas, the acquisition of California and other territory by the Mexican War and, later, the Gadsden Purchase, changed not only our geographical but our phytographical boundaries. Individual and government explorations were pushed not only into the newly-acquired Territories, but our older possessions were more thoroughly examined, and materials came in at such a rate that to continue the Flora as then commenced would require an appendix larger than itself. Each of its authors then occupied himself with studying the new materials as they came to hand, and in giving their results to the scientific world. This interruption of the Flora was followed by the publication, by both Dr. Gray and Dr. Torrey, of a series of most valuable botanical memoirs, sometimes conjointly, but oftener separately. These may be found in the various Government Reports, and in the transactions of the American Academy of Arts and Sciences, of the Smithsonian Institution, and other learned bodies.
The most conspicuous of these contributions to our North American Botany by Dr. Gray are, "Plantæ Lindheimerianæ" giving an account of the plants collected in "Western Texas, by F. Lindheimer; in this memoir he was aided by Dr. George Engelmann; "Plantæ Fendlerianæ Novi-Mexicanæ" a description of the plants collected in New Mexico, by Aug. Fendler; "Plantæ Wrightianæ Texano-Neo-Mexicanæ" describing the extensive collections of Charles Wright, A. M. This paper is in two parts, and illustrated. Another memoir, "Plantæ, Nbvæ Thurberianæ" though shorter than those already named, is important as describing an unusual number of new genera and species. These contributions are not confined to the working up of the materials of the particular collections of which they treat, but in many cases whole genera are elucidated and rearranged in a masterly manner.
These memoirs are mentioned out of their chronological sequence, as they may be considered, as well as those published by Dr. Torrey, as material accumulated for the use of whoever may undertake that Flora of North America for which botanists are hopefully looking.
In 1848 appeared the first volume of "Genera Floræ Americæ Boreali-Orientalis Illustrata" or, as it is best known, under its shorter title, "Gray's Genera." The object of this work was to give a typical specimen of one or more species of each genus of North American plants, with accurate analyses. The drawings for this work were made by Isaac Sprague, and for accuracy of detail and neatness of execution have not been excelled. Two volumes, containing one hundred plates each, were published, when, to the regret of all American botanists, the publication was suspended for the same reasons that we have given for the discontinuance of the "Flora."
The most voluminous and in some respects the most important of Dr. Gray's contributions to science relate to extra-American botany; we refer to the "Botany of the United States Exploring Expedition."
