Part II] Hole : Regeneration of Sal (Shorea robusta) Forests 5 
It will be seen that the average annual height growth has remained 
almost constant between the ages of 2 and 8 years and up to a height 
of 22 feet. Chemical and mechanical analyses of the soil in the Dehra 
Dun Garden are given in the Appendix, Samples A and B. 
Experiment II. 
Object of Experiment. To determine the effect of a layer of dead leaves 
on germination and early growth of seedlings. 
7. In an experiment carried out in 1913 by the writer, it was shown 
that a layer of dead sal leaves in the surface soil is injurious to germination 
and the development of sal seedlings and this was ascribed to bad soil 
aeration caused by the increased water content and the addition of organic 
matter to the soil. (Indian Forester, XLI, pp. 353, 354, October 1915, 
and Ind. Far. Rec. V, 4, Part II, pp. 69, 78, 1916.) 
In an experiment carried out in 1914-15, Mr. R. S. Troup also showed 
that dead sal leaves were decidedly injurious, but he attributed the 
effect mainly to the mechanical action of the leaves (Indian Forester 
XLII, pp. 57-60, 1916). 
The present experiment was undertaken with the object of obtaining 
more definite information regarding these two actions. 
The present experiment was divided into 4 parts designated (a) to 
(d) below. 
(a) To test the mechanical action of dead leaves » 
8. In June 1916, six large porous pots were sunk in the soil, in the 
open, in the Dehra Experimental Garden so that their upper edges pro¬ 
jected one inch above the level of the surrounding soil. Each pot 
measured 2 feet high and 2 feet in diameter at the top and had three 
lateral drainage holes at the base each of f inch diameter. The pots 
being sunk and thus brought into close contact with the soil on the sides 
and at the base, the temperature of their contents would approximate 
to that of the surrounding soil. On June 8th, 1916, two of these pots 
(1-2) were filled with clean river sand brought locally from the Song 
river, and the remaining four pots (3-6) were filled with loam brought 
from the local Lachiwala sal forest. A layer of dead sal leaves, 6 leaves 
thick, was then laid on the surface of the soil in pots 1-4 inclusive. In a 
well-stocked sal forest, the annual leaf-fail forms an average layer 4-5 
leaves thick, and below this there is usually a thin layer of raw humus 
from the previous year’s supply. A layer of 6 leaves, therefore, is believed 
to approximate to that found in the natural forests. On June 20th, 
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