MIXED FORMATIONS IN TIME. 31
From the oecologieal point of view the great difference between
Europe and America on the one hand and India on the other is that
the former really have no habitat which even approximately corres-
ponds to the Indian monsoon habitat, with its succeeding eight
months of drought. This is the one great factor which has been, in
certain aspects, unconsciously ignored, and which cannot be ignored.
Seasonal differences are found in other habitats, but I believe it must
be admitted that they are much less profound and far reaching than
those in the monsoon habitat as we see it in its typical development.
When we examine such a habitat we often find that during the year two (or it may be three) profoundly different sets of conditions are met with in the same spot. Practically these constitute two (or three) entirely different habitats . First a condition when both soil and air may be almost continuously water saturated for about 3 months, and when comparatively delicate mesophytic plants may flourish. If towards the end of this period the soil becomes com- pletely water-logged, aeration soon becomes very deficient, which upsets the equilibrium in such a way that swamp conditions arise. Whether this happens or not, and how soon, will depend, amongst other things, on the sub-soil drainage. In any case at the close of the monsoon the soil and air both gradually dry, and after about a month a period of seven months intense and absolute drought sets in. During this time the formation to be met with must be regarded as most markedly xerophytic. Only plants with some well defined x9rophytic equipment can survive.
Now according to our present conceptions we think of any parti- cular small area, if reasonably stable, as being occupied by one forma- tion, though doubtless it may have different seasonal aspects and different floristic composition at different times. Still, essentially, we think of it as a unit*
But in such habitats as have been described above such a concep- tion often appears absolutely untenable and absurd. Examining a hypothetical small area, such as I have mentioned, it may be supposed to be xerophytic bushland in the months of April and May, equally well to be a meadow* with scattered bushes in July and August, and possibly also to be a marsh in September and October.
The idea of 14 succession ” is of course familiar, but this is not
- I use the term meadow here and elsewhere merely in an illustrative
manner, without wishing to imply : that there is anything in the plains of India which exactly corresponds to the ‘ meadow ’ of North Temperate coun- tries, which is in fact very doubtful.
