group includes a series of critical reviews of important scientific publications, and of historical accounts of the lives and labors of workers in botany; and the fourth group a number of papers which owe their existence to the discussions that followed the publication of Darwin's "Origin of Species." The present volumes contain a selection of papers from the third group, with a few essays on subjects of general interest to botanists. Most of these papers, unlike those of the other groups, which are still in the market, have long been out of print, and have not been incorporated in any recent publication. The selections have been made with the thought of presenting, as far as might be, a view of the growth of botanical science during the fifty years through which the papers run a period which, as the editor observes, is marked by the gradual change of ideas among naturalists upon the origin and fixity of species that has broadened the field of all biological investigation. The period was also characterized by a great increase and diffusion of the knowledge of botany in the United States, and by the growth of a body of earnest, energetic American botanists, who have not only given vigor to the study and inspired interest in it through all the schools, but have also contributed to exalt the reputation of American science; and these botanists are, and are what they are, almost wholly by reason of what Prof. Gray and his books taught them.
A glimpse of the condition of botanical study in the United States at the beginning of Prof. Gray's fifty years is afforded in the first of the papers, which is a review of the second edition of Lindley's "Natural System of Botany," published in 1836-'37. The intimation that "we do not intend to engage in a defense of what is called the natural system of botany" indicates that that system had not yet fully conquered acceptance. Still, the author assumed that the science could by no other method be successfully and philosophically pursued, and added: "The few persons who remain at this day unconvinced of its advantages are not likely to be affected by any arguments that we could adduce. A somewhat larger number may perhaps be found in this country who admit the importance and utility of the natural arrangement in the abstract, but decline to avail themselves of the advantages it affords in the study of plants, because, forsooth, it is too much trouble to acquire the enlarged views of vegetable structure which arc necessary for the application of its principles." But the system had grown in favor during the preceding six years. Twenty years later, in the review of Henfrey's "Botany," 185*7, we are given this picture of the condition of botanical instruction here: "While in England botany is scarcely an academical study, here it pertains to collegiate and academical instruction where it is taught at all. In Europe not even an apothecary can be licensed without passing an examination in botany; in the United States, we believe, it forms no part, at least no regular part, of the medical curriculum; no medical school has a botanical chair; and no knowledge whatever of the science of the vegetable kingdom, which supplies the materia medica, is required for the degree of Doctor in Medicine!" With botanical chairs in a large number of our leading universities and schools, filled by experts who are engaged in original work and encourage it in their students; and pupils in high schools knowing more of the structure and qualities of plants than the doctors Prof. Gray describes, we of the present time have no reason to be ashamed of the advance that has been made. From these almost elementary considerations, the reviews and essays follow the series of publications in the science and the course of discussion over the whole scientific world, while having an eye primarily to America, including such subjects as Van Mold's observations of the cell; De Candolle's theories of variation and distribution and of the origin of cultivated plants, in reviewing which the author displays the sharpness of his discernment and the thoroughness of his knowledge regarding American plants; Radlkofer's and Henslow's studies in fertilization; the principles of nomenclature and the definition of species; several local floras and special studies, never forgetting those that are primarily of American interest; and those studies in which Prof. Gray so greatly supported and aided Darwin, relative to variation and the origin of species. In these notices, while some of them seem to bristle with technicalities and run to details, the techni-
