NOTES OX DIPTEROCAEPS. 43 



But if the fires be repeated too soon any occasional advantage 

 is lost*. And after all what is the advantage where conditions are 

 favourable to Sal, for there considerably over ninety-nine per cent 

 of the seeds which fall must fail for want of room. 



It cannot be that the liability of Sal or Dipterocarpus forests 

 to fires assists at all in maintaining pure forest other than perhaps 

 as Haines suggests in destroying fungi. So much is this recognised 

 that every Indian forester of experience advocates fire protection, 

 as a principle. But fire applied not more frequently than, say, 

 triennially beyond the edge of pure forest may assist the Sal or 

 Dipterocarpus in extending by clearing the way for the seed and 

 damaging the competitors. Unfortunately forest fires where likely 

 to occur, are annual. And under this view, the failure of the 

 Malayan Shoreas to make pure forests is scarcely to be ascribed to 

 their freedom from them. 



It is on deep open soils that Sal makes the pure forests — soils 

 such as happen to be peculiarly well developed by rapid rivers from 

 out of the rocks of the Himalaya, soils where the water may sink 

 in dry periods in such a wayf as to injure many plants which com- 

 pete elsewhere. Sal finds on these soils the combination of yet 

 unanalysed conditions ideal to it: and obviously it has a peculiar 

 physiological adaptation to their nature to which its success may be 

 ascribed. This physiological adaptation it shares somewhat with 

 Shorea assamica: for Shorea assamica makes its pure forests on just 

 the same kinds of soil. 



Sal seedlings have a wonderful power of replacing the primary 

 stem if it be lost, even right from the axils of the cotyledons. So 

 far I have seen nothing like it in the Malayan Shoreas. Not once 

 only can the seedling make good the leader, but it may renew it 

 again and again through some years. Hole has illustrated this 

 process in three places (Indian Forest Records, v, part 4-, 1916, 

 plate 1; Indian Forester, 1916, plate 23, p. 336; and Agricultural 

 Journal of India, Indian Science Congress Xumber, 1916, plate 1.) 



This loss of the leader is usually caused by something which, 

 is not a forest fire, though forest fires may of course cause it; and 

 in at least ninety per cent of cases it comes from some under- 

 ground influence acting through the root. Hole finds that the mix- 

 ing with the soil of leaves, especially of Sal leaves, increases it. 

 and he suggests that a- toxic body is produced in the process of 

 their decomposition directly or indirectly. If this be so, then light 

 forest fires by removing the leaves on the forest floor may do good. 



For the destruction of the Sal forests at the foot of the Himalaya 

 between the rivers Gandak and Teesta, by repeated firing, sec my, note in 

 the Joumalof the Asiatic Society of Bengal, 1916, p. 267. 



fCf. Milward's statement {Indian Forester, xxviii, 1803, p. 411) that 

 under excellent Sal in Oudh the water may be 40 feet down. 



R. A. Soc, No. 79. 



