124 INDIAN FOREST MEMOIRS. 



the roots are thus inactive, the leaves may be actively transpiring moisture 

 under the influence of bright sun-light and dry air-currents. The leaves and 

 branches of woody plants may thus become completely dried up and killed, in 

 the same manner as in a case of drought. 

 (b) Directly by the low temperature of the air in contact with the aerial leaves, twigs 

 and branches. 



The first mode of action can often be recognised in the forest by the fact that those 

 aerial portions of a plant tend to be injured first which are furthest removed from the water 

 supply ascending from the roots, i.e. the base of the leaf and those parts of the lamina 

 nearest the main nerves are often found to be uninjured and green when the rest of the 

 leaf is shrivelled and brown, while the terminal twigs and branches tend to die back first. 



On the other hand, the second mode of action can often be recognised by the fact that 

 those parts of the plant are most injured which are in contact with the coldest air, irrespect- 

 ive of their position at the base or apex of the plant. Thus those leaves or portions of 

 leaves which are shaded by neighbouring leaves and thus protected from radiation will be 

 often found to have escaped damage when the rest of the leaves have been killed. In grass- 

 lands unrestricted radiation tends to produce a layer of cold air just at, or immediately 

 above, the level of the grass and that radiation is chiefly responsible for the frost damage 

 done to woody plants in the grasslands now under consideration is often clearly indicated 

 by the fact that the leaves and twigs situated just at, or immediately above, the level of the 

 grass tend to be damaged first, although they are not necessarily at the apex of the plant. 



103. With reference to the treatment of this 

 type of grassland, therefore, it is obvious that we may either try to reduce radiation which is 

 chiefly responsible for the failure of Sal to establish itself in areas where the soil is generally 

 suited for it, as indicated by the prevalence of the grass Saccharum Narenga, or we must 

 introduce frost-hardy and xerophilous species which are able to thrive under the conditions 

 of the habitat. 



The injurious action of radiation might be modified — 



(a) By clearing lines through the surrounding forest and thus improving the circula- 



tion of air. 



(b) By irrigating and thus keeping the soil moist which would result in increasing 



the quantity of water vapour in the air and thus in decreasing radiation. 



On the other hand, if these measures are impracticable, the most suitable indigenous 

 frost-hardy and xerophilous species for afforesting these grasslands is almost certainly the 

 khair, Acacia Catechu. Another species which would probably be of value in establishing 

 woodland in such places is Zizyjjhus Jujuba. 



Two exotic species which it is believed might be successful are Cinnarnomum Camphora 

 and Eucalyptus citriodora both of which were observed to successfully survive the excep- 

 tionally severe winter of 1904-05 in frosty grasslands in this locality. 



i 124 ] 



