56 THE STRUGGLE FOB EXISTENCE. 



As regards the relative effects of frost on the various species 

 composing a crop, they will be directly proportionate (i) to the ex- 

 panse of the leaves and the roughness of the buds, leaves, and in- 

 ternodes; (ii) to the thinness of the leaves; (iii) to the quantity of 

 water in the cell sap as compared with solid substances; (iv) to the 

 looseness of texture of the active tissues ; (v) to suddenness of thaw; 

 (vi) to the thinness and late formation of the outer covering of dead 

 bark (the rhytidome); (vii) to shallowness of rooting ; and (viii) to 

 the quantity of watery vapour in the atmosphere. We may hence 

 deduce the following corollaries, granting always that other cir- 

 cumstances are equal: (a) the more active the vegetative process- 

 es during the season of frosts, the more sensitive the tree; (b) the 

 greater the number of dormant buds, the hardier the species; and 

 (c) the more generous the growth of a young plant, the slighter its 

 power of resistance. 



Besides influencing the development of individuals of the various 

 species, temperature also affects their ability to bear flowers and 

 fruit (see Condition XII, a and b). 



(b) Damp and drought. Here also only extremes have any ac- 

 tion. For instance, teak seems to thrive best under a mean annual 

 rainfall of from 50 to 120 inches, but does not disappear till the fall 

 decreases to about 24 inches. Even the range of rainfall of sal ex- 

 tends roughly over 80 inches, viz., from 40 to 120. 



In the dry climate of Rajputana the Anogeisuss pendula easily 

 gains the ascendancy over all other species. The jand (Prosopis 

 spicigera) finds no rival or compeer in the dry rakhs of the Pun- 

 jab. 



Under damp must be included, besides rainfall, also relative 

 humidity. The sal will acquire its finest dimensions in the hot 

 steamy valleys of the Lower Himalayas, but refuse to grow in 

 Chanda and other places where, although the temperature during 

 the hot weather is scarcely higher, nightly dews are neither heavy 

 nor occur during any considerable part of the dry season. 



This statement is supported and further illustrated by the follow- 

 ing table which gives the figures of the mean relative humidity at 

 the several places mentioned in it during the months of March 

 June, when sal is putting forth and developing its new shoots and 

 is most in need of moisture. The table also explains how, owing 

 to an excess of moisture, sal is unable to extend itself as far east as 

 Sibsagar and Silchar, and that, therefore, it can have too much as 

 well as too little atmospheric humidity. 



