Page:Popular Science Monthly Volume 21.djvu/870

852 attention that so remarkable an instrument deserves. The staining and injecting of objects are as fully treated of as the size of the book would permit, and a colored frontispiece is introduced to show the effect of double-staining on wood-sections.

The author exhibits commendable fairness in his treatment of American microscopists, and of instruments made on this side of the water, especially the wide angled objectives of Spencer, of Geneva, and Tolles, of Boston. He says: "It is only recently that American objectives of the widest aperture have found their way into the author's hands. Their definition is marvelous." Medium angles have been advised for students' use, because they can be employed without much previous knowledge or difficulty; but for all purposes of scientific investigation wide apertures give more satisfactory results.

Many of the illustrations have been photographed by the author from nature and then cut in wood. Some of these are very fine, as, for example, the sting and poison-bag of the bee and wasp, the digestive apparatus of the water-beetle and of the blow-fly, and various other natural objects.

The rapid strides that have recently been made in the manufacture of cheap and very good working microscopes have created a demand for works of this character, and Mr. Davis's book supplies a real want.

recent publication of the Smithsonian Institution contains the scientific and common names of 1,384 plants found in the vicinity of the national capital, together with their time of flowering, and in many cases the localities where they may be sought for. Appended arc a check-list and a map of the region for fifteen or twenty miles around the city of Washington. The labor of preparing a "flora" of even a limited space of country is much greater than might be supposed, and in the present case many able and active botanists have cooperated with the author, as well as many energetic amateurs. The appearance of this work recalls to mind a remark of the late Dr. John Torrey, that in his younger days he attempted to prepare a flora of the City Hall Park, New York. At that time there was neither post-office nor court-house there. Even in that small space he met with so many and such a rapidly increasing number of varieties and species that he was compelled to abandon the project. From its cosmopolitan nature New York naturally receives fresh additions to her flora annually from every quarter of the globe. Even in Washington there has been a considerable change in the flora since the "Prodromus" appeared half a century ago. Of the 860 distinct plants enumerated therein, the author has succeeded in identifying 708, while nearly as many more have been added. Although the primary aim of the author was to furnish a guide to botanists in exploring the locality, it will serve as an aid to beginners in practical botany elsewhere. An appendix is added, especially addressed to the latter class, and containing among other things suggestions regarding identification of plants, collection of plants, preservation of plants, making an herbarium, care of duplicates, exchanging specimens, etc. On the first of these points the author remarks that "a young botanist's struggles with botanical keys can only be sympathized with; they can scarelyscarcely [sic] be aided by any general directions, and there is no more effectual drill than the persevering effort to identify, by the aid of a key, a plant to which he has no clew. It should be the ambition of every such beginner to analyze in this manner all the plants of his local flora." The less help he receives the better, and, the more ignorant the beginner is at the outset, the better will be his ultimate acquaintance with botany if he perseveres in the work. In regard to localities the writer very appropriately remarks that "in many respects the botanist looks at the world from a point of view precisely the reverse of that of other people. Rich fields of corn are to him waste lands; cities are his abhorrence, and great open areas under high cultivation he calls 'poor country'; while on the other hand the impenetrable forest delights his gaze, the rocky cliff charms him, thin-soiled barrens, boggy fens, and irreclaimable swamps and morasses are for him the finest land in the State. He