of the mode in which the
floras of islands and of continents have been formed gave rise to
important speculations by such eminent botanical travellers as Charles
Darwin, Sir J.D. Hooker, A.R. Wallace and others. The connexion
between climate and vegetation has also been studied. Quite recently
under the name of "Ecology" or "Oecology" the study of plants in
relation to each other and to their environment has become the subject
of systematic investigation.

The subject of palaeontological botany (see PALAEOBOTANY) has been
advanced by the researches of both botanists and geologists. The nature
of the climate at different epochs of the earth's history has also been
determined from the character of the flora. The works of A.T.
Brongniart, H.R. Goeppert and W.P. Schimper advanced this department of
science. Among others who contributed valuable papers on the subject may
be noticed Oswald Heer (1809-1883), who made observations on the Miocene
flora, especially in Arctic regions; Gaston de Saporta (1823-1895), who
examined the Tertiary flora; Sir J.W. Dawson and Leo Lesquereux, and
others who reported on the Canadian and American fossil plants. In Great
Britain also W.C. Williamson, by his study of the structure of the
plants of the coal-measures, opened up a new line of research which has
been followed by Bertrand Renault, D.H. Scott, A.C. Seward and others,
and has led to important discoveries on the nature of extinct groups of
plants and also on the phylogeny of existing groups.

Botany may be divided into the following departments:--

1. Structural, having reference to the form and structure of the various
parts, including (a) Morphology, the study of the general form of the
organs and their development--this will be treated in a series of
articles dealing with the great subdivisions of plants (see ANGIOSPERMS,
GYMNOSPERMS, PTERIDOPHYTA, BRYOPHYTA, ALGAE, LICHENS, FUNGI and
BACTERIOLOGY) and the more important organs (see STEM, LEAF, ROOT,
FLOWER, FRUIT); (b) Anatomy, the study of internal structure, including
minute anatomy or histology (see PLANTS: _Anatomy_).

2. Cytology (q.v.), the intimate structure and behaviour of the cell and
its contents--protoplasm, nucleus, &c.

3. Physiology, the study of the life-functions of the entire plant and
its organs (see PLANTS: _Physiology_).

4. Systematic, the arrangement and classification of plants (see PLANTS:
_Classification_).

5. Distribution or Geographical Botany,