Pursuing this line of enquiry, we may endeavour to trace the descent through the ages of our present plants from bygone types; and coming at length to the still remote time--as measured by human standards--when the plants which now grow appeared on the Earth’s surface, we may try, from a study of their present distribution and of the distribution of their remains in regions where they are no longer found living, to determine their area of origin, and to trace the date and course of the migrations by which they reached our country. In the case of the British Isles, geological considerations play a leading part in such investigations, these islands being but outlying hummocks of a great continental area, at times joined to the main land-mass by a slight upward movement of the Earth’s crust, and anon cut off from it by a movement of depression. In this connection also we may be led to investigate the means by which plants spread, and especially their capacity for crossing barriers of the various kinds indicated in our brief study of deserts in the previous pages--the serious barriers offered by water-channels, or others equally difficult to negotiate produced by areas of uncongenial soil, by mountain ranges, or by forests. This will involve especially a study of seeds and the interesting phenomena of seed-dispersal. Again, the most popular branch of botanical study in England is _Floristic Botany_, which traces the distribution within our area of the various species composing its flora; and with it is necessarily associated a study of the plants themselves so far as the characters are concerned, by which they may be distinguished from each other. This last is the province of _Descriptive Botany_. The study of local distribution, if conducted intelligently, will greatly assist in solving problems relating to the migrations and routes by which the existing flora reached its habitats. Once more, we have already from Farleton Fell observed that plants do not grow higgledy-piggledy over the country, but are arranged in more or less definite societies depending on similarity of climate, soil, and other external conditions. Studied from this point of view, the flora resolves itself into a series of communities, each requiring a certain set of conditions for its continued welfare. The study of these inter-relations between plants and their environment, and of the types of vegetation resulting from the grouping together of plants requiring similar conditions, is the province of _Ecological Botany_. Again, the _morphologist_ deals with the forms of the organs of plants, and the changes which these undergo in different plants, while the _anatomist_ investigates their minuter structure.