Page:The Journal of Indian Botany, Volume III.djvu/64

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During the last fifteen years great strides have been made in the study of Oecology. A large amount of work has been done, both in Europe and America, to increase our knowledge of plant formations and associations. In most cases, and especially where large areas have been studied including various different formations, we are of opinion that the analysis of the vegetation has not been as exact as it should be, while in other cases it has seldom been possible to decide the precise relation between the plant and the various differing factors of the habitat. For the tropics the recent papers by McLean (4) give some interesting analysis of physical factors but no detailed analysis of the vegetation is attempted.

It is of course abundantly clear that the different aspects of vege- tation depend ultimately on physical factors such as water content of the soil, humidity of the air, light and temperature, but it is not always clear which of these factors is dominant in particular cases.

So far as the authors are aware, not very much work has been done with a view to elucidating the causes,, often rather obscure, which lead to somewhat marked differences of vegetation, in an area where the physical factors at first sight appear uniform, and where the differ- ences are, in the main, rather floristic than definitely oecological ; that is to say where the whole area must be held to belong to the same formation and association, although the communities * are different.

Such cases are very frequent in the vicinity of Ahmedabadf and it appeared to the writers that a more or less detailed study of one typical case might throw light on the problem as a whole. An area was selected which had been under casual observation for about 6 years. During that time nothing had been done to disturb the natural development of the vegetation and no marked changes seamed

The term “ Community ” is used here to denote a unit next below that generally understood by an “Association.** It thus corresponds approximately to “ Variety of Association ** as defined by Warming (10) or to ^Society” in the sense understood by Clements (2).

t Ahmedabad is about 50 miles N.E. of the Gulf of Cambay. Lat. 23°.2' N. Long. 72*39' E.