Special plantations of selected families must depend for their constituency upon the loca tion of the garden. Thus it would be possible to form a collection of palms in a tropical garden and one of pines or willows in a temper ate climate. Geographical plantations may take any given district by variously arranged plan tations.
Still another group of plantations is being made in some gardens to illustrate types of habit and structure. Some of the principal groups to be illustrated in this manner are parasites, which draw nourishment from the living bodies of other organs; saprophytes, which live on decaying organic matter; xero phytes, plants adapted to living under the driest conditions; plants with structures serv ing as a protection against animals. Forms of propagation and reproduction, methods of dis semination of spores and seeds, etc., also serve as subjects to be illustrated by separate groups.
The collections grown under shelter and in conservatories are generally grouped in such manner that species are partly assembled with regard to their climatic requirements, and partly according to their relationships. Thus a house may be devoted to tropical plants, or to tem perate plants, or may contain only orchids, palms, ferns, cacti or succulents, or other special groups.
The part of the vegetable kingdom which may not be cultivated may be represented in a museum by dried specimens, material in pre serving-fluids and dissections of various kinds. Here again the arrangement may be upon the basis of natural relationship, or upon the basis of economic usefulness. The species which formed the vegetation of the previous geological periods are represented by fossil specimens, completing the history of the plant-world so far as it is known, and yielding suggestions as to the descent of the present types.
Two general educational purposes are served by an institution of this character. Its collec tions are arranged to present information on the form, relationship, mode of life, habit and general biological character of the principal types of vegetation, in such manner as to be capable of comprehension by persons unac quainted with the technical aspects of the sub ject. Further interpretation of such facts may be made by means of books, journals, lectures, etc., devoted to this branch of work and study.
The material accumulated for the exploita tion of popular knowledge of plants also af fords an excellent basis for the induction of students into the more strictly scientific aspects of botany; and when such material is supple mented by laboratories furnished with appara tus, microscopes and other instruments of precision, the activities of these students may be carried beyond the frontiers of the subject into the investigation and discovery of new facts and phenomena. This extension of the
boundaries of knowledge concerning the plant world may be carried on to advantage only when a library is at hand containing all of the more important literature bearing upon the subject.
Botanical gardens owe their origin to the needs of medical science, in accordance with which species showing valuable medicinal prop erties were grown in convenient places.
The first authentic record of the introduc tion of medicinal plants into cultivated plots of ground dates no farther back than the time of the elder Pliny (23-79 A.D.), who writes of the garden Antonius Castor, at Rome, in which were grown a large number of medicinal plants. This step, however, may have been taken much earlier by the Greeks, Chinese or Mexicans. Later the Benedictine monks of northern Italy paid great attention to the growing of remedial herbs, and devoted an important proportion of the monastery gar dens to this purpose. This practice was also carried beyond the Alps, and in 1020 a garden was in existence at the monastery of Saint Gall, in Switzerland, not far from Lake Con stance, which contained 16 plots occupied by medicinal plants. A garden of this character was founded 1309 at Salerno, and another at Venice 1330.
The 16th and 17th centuries witnessed the foundation of many gardens in England, France, Germany, Holland and Sweden, some of which have had a continuous existence to this day. The garden of Bologna was founded 1568; Leyden, 1577; Leipzig, 1579; Montpellier, 1596; Paris, 1597. The last named was organ ized for the determination of ((what variations were possible in the style of bouquets worn at the royal courts.* Then followed the estab lishment of thegardens at Giessen, 1605; Jena, Strasburg, 1620; na, 1629; Oxford, 1632; Upsala, 1667; Chelsea, 1680.
The number of these institutions at the present time is nearly 300, only a few of which, however, are devoted to the more important purposes named above. Many botanical gar dens are merely municipal parks in which some attempt is made to exhibit special groups of plants, and are devoted chiefly floricul ture. Others are almost entirely experiment stations for the exhibition and testing of eco nomic species, while still others find their chief usefulness as an aid in teaching botany in schOols and colleges. For the educational vahie of botanical gardens, consult Monroe, 'Cyclopedia of Education.)