The second floor is given over to an exhibit of types of all of the more important families and tribes of plants, from the simplest and most minute, to the highest and most complex. Specimens, models, fruits, seeds, drawings and photographs are used to bring the principal facts clearly before the observer. A set of swinging frames running parallel to the cases containing the types of the flora of the world, are used to display specimens of the plants found within a hundred miles of New York City. A number of special microscopes have been constructed for the purpose of forming a perfect exhibit, which will enable the visitor to see some of the more salient features in the minute structure of some of the plants in the cases. [Illustration: THE MUSEUM.] The third floor contains the library, herbarium and laboratories. The library occupies a stack room extending to the rear of the middle of the building, two small storerooms and a large circular reading-room, under the illuminated dome. Here are assembled the botanical books of Columbia University, as well as those accumulated by the Garden, now numbering more than eight thousand volumes, with no reckoning of unbound separates and pamphlets. The collection of botanical periodicals is nearly complete, and the library is especially rich in literature concerning the mosses, ferns, and the flora of North and South America. The main herbarium occupies a room in the east wing, eighty-five by forty-seven feet, and connected with it are storerooms and offices adequate to its administration. Windows on all sides of the main room and skylights give ample illumination. The number of mounted specimens on the shelves is not less than three quarters of a million, including the herbarium of Columbia University, which is deposited here in accordance with the agreement between the two institutions. The collection is especially rich in fungi, embracing the collections of Ellis and other eminent mycologists. A large amount of material of great historic value in connection with the work of Dr. John Torrey and the earlier botanical development of America is included. Accessions are being made to the herbarium at the rate of fifty to a hundred thousand specimens annually. [Illustration: IN THE FOREST.] The laboratories consist of a series of rooms facing northward and westward, with special facilities for taxonomic, embryological and morphological investigations. Physiological and photographic darkrooms, the experiment room for living plants and chemical laboratories offer especially ample opportunities for the record and development of practically all phases of plant physiology. The laboratories, library and herbarium are open to the graduate students from Columbia University, in addition to those from other institutions of learning who may register directly at the Garden. The latter, in return, have the privileges of students at Columbia University.