52 THE STRUGGLE FOE EXISTENCE. 



standing in the midst of evergreen neighbours can survive on 

 the sole condition that from the earliest years they grow more 

 rapidlv, not only upwards but also laterally, than their compa- 

 nions. 



Regarding the rate of growth in height of our various species in different parts of 

 their respective habitats no trustworthy information isasyet available. In a continent 

 like Inilia, we are bound to obtain widely differing figures for one and the same spe- 

 cies according to the locality and the region in which it may grow in each case. Un- 

 til such information is forthcoming, it will be extremely useful to construct compa- 

 rative diagrams of the relative rapidity of growth of different species standing toge- 

 ther in one and the same forest. 



The varying rapidity of growth of each species should be delineated by a curve 

 with its. generating rectangular co-ordinates, the abscissa representing the age, and 

 the ordinate the height of the average tree at that age. Figure 1 is such a compara- 

 tive diagram for two trees, A and B ; the curves are traced by means of the respective 

 heights attained at 10, 20, 30, 40, 50, 60, 70, 80, &0, and 100 years of age. The 

 diagram shows at a glance that up to the age of i9 years B grows faster than A ; at 

 50 it is overtaken by the latter, which then gets away from it. The rapidity of growth 

 of A is slow for the first ten years, then becomes rapid up to seventy years, after 

 which it decreases gradually, and becomes almost stationary. B, on the other hand, 

 grows up rapidly at once, until it reaches tha age of 50 years, and then makes little 

 head afterwards. In the diagram -^ in. on the axis of X, or the horizontal line, re- 

 presents one year, and similary -^ in. on the axis of Y, or, which comes to the same 

 thing, on the perpendicular line, represents one foot. 



Similar diagrams may be constructed to represent relative rapidity of lateral exten- 

 sion. 



IX. MAXIMUM HEIGHT ATTAINABLE. This condition finally de- 

 cides what trees, out of those that survive up to a certain stage of 

 growth, shall form the crop, or, if there are species present that are 

 shade-enduring enough, to constitute a permanent undergrowth, its 

 upper story. Of the companions of sal there are only the Termi- 

 nalias, some Albizzias, Adina cord/folia, some Eugenias, and half 

 a dozen other species which attain the same height as that noble 

 tree, and which, therefore, compete with it for a place in the lofty 

 leaf-canopy of the full-grown forest. In Central India (including 

 Northern Bombay), teak is generally a small tree, and is hence, 

 wherever more powerful countervailing conditions do not prevail, 

 easily beaten by its taller companions. Deodar is, outside the region 

 of the firs, the tallest tree in the forests where it grows; whence 

 its gregariousness wherever other circumstances, such as soil, mois- 

 ture, &c., are favourable. Again, Mesua ferrea is, with the excep- 

 tion of Altingia excelsa, the tallest tree in the large areas which it 

 covers almost by itself in Assam. The teak in Burma, and the 

 Artocarpus Chaplasha in Assam, although unfavourably circum- 

 stanced in many other respects to struggle for existence with their 

 companions, are able to hold a permanent pla ce in their midst ow- 



