44 INDIAN FOREST MEMOIRS. 



months a general cessation of activity is more or less marked and is apparently caused 

 mainly by the low temperature. 



As regards an explanation of the periodicity shown by the various species it is highly 

 desirable that statistics should be obtained showing, for the different classes of soil, the 

 actual average water-content of the surface layers of bare unworked soil monthly throughout 

 the year and especially during the period October to May inclusive. Such statistics would 

 indicate the net result of the opposing factors of, on the one hand, rainfall, dew deposition 

 and the raising of the subsoil water by capillarity, and on the other hand of loss through 

 percolation and evaporation at the surface, and this net content is of extreme importance 

 for vegetation. 



Unfortunately no statistics of this nature appear to be at present available in India, 

 but observations on this point will now be made at Dehra Dun in connection with the study 

 of the cecology of Sal. 



A point which has been frequently noticed in connection with several of the species 

 dealt with in this paper is that, in areas where the grass has been cut or burnt, vegetative 

 activity commences earlier than it would otherwise have done and the growth of the young 

 shoots is far more vigorous, especially during the period February to May, than in areas 

 which have not been cut or burnt. Forest Officers are well acquainted with this phenomenon 

 and know that areas burnt in the cold season are covered with a good crop of green grass 

 in the ensuing hot weather, when there are few or no green shoots to be seen in protected 

 areas. The clearing away of the old grass and dead leaves by fire enables the dew and 

 rainfall to at once penetrate the soil instead of being obstructed by, and evaporated from, 

 the old grass, and thus prevented from finding its way into the soil and becoming available 

 for the grass roots, while it also removes the injurious shade which to a considerable 

 extent retards the development of the young shoots. 



ofveXT 41 ' In ^e area cons idered in this paper 



tion. examples of almost all the main types of vegetation mentioned in paragraph 26 above, both 



of grassland and of woodland, are to be found. 



Hygrophilous grassland is represented by well-developed reed-swamp communities of 



Phragmites and Arundo and perhaps also by the wet Savannah Erianthus, while a type 



of woodland which should possibly be ranked as intermediate between mesophilous and 



hygrophilous is represented by some remarkable swamp forests containing such species as — 



Carallia lucida. -. 



Cyclostemon assamicus. I 



D - „t„jl„ • ■ > Of the Indian Evergreen Forest tracts. 



Bischojia javanica. i & 



Calamus tenuis. - 



As well as such temperate species as Quercus incana, Acer oblongum and Hedera 

 Helix. 



These swamp areas however are of comparatively limited extent and are not dealt 

 with in this paper. 



[ 44 ] 



