44 THE 8TBUGGLE FOE EXISTENCE. 



(iv) On its ability to re-form at once a strong leader, when the 



orginal one has been broken or killed ; 

 (v) On its ability to replace sufficiently early a lost important 



limb ; and 

 (vi) On the vitality of the bark, i.e., its readiness to form and 



close over wounds and bruises. 

 All these points are self-evident, and require no explanation. 



(g) Climbers. The remarks made under this head in the two 

 preceding Cases apply with equal force here. Besides this, it may 

 be added that climbers are in no sense selective as regards the 

 species of tree along which they rise above ;the ground, except that 

 those which climb only by means of tendrils or adventitious roots 

 will seldom be found on trees with smooth or exfoliating bark, 

 such as Homalium tomentosum, Boswellia serrata, &c. Usually 

 climbers are confined to rich or at least moist soils and the edge of 

 slopes, and are hence peculiarly destructive to species that affect 

 such soils and localities. 



IV. COMPLETENESS OF THE LEAF-CANOPY ; RELATIVE DENSITY 



AND SHAPE OF CROWN, AND RELATIVE CAPABILITY OF PERSISTING 



UNDER OR PUSHING UP THROUGH COVER. It will be noticed 

 that the second clause of this heading is additional to what ap- 

 peared in the two previous cases. Its -necessity is evident. With 

 only a single species in the crop, all the plants are necessarily 

 equally able or equally unable to persist under or push up through 

 cover overhead ; but the moment a second species enters the crop, 

 the relative ability of the two in this respect becomes a most im- 

 portant element in the natural struggle for existence and has 

 hence to be considered. Moreover, the relative density and shape 

 of the crown of any species in question regulates, to a considerable 

 extent, its proportion and distribution in a mixed crop. 



As a rule, the denser the foliage of a species is, the more shade- 

 enduring will young individuals of it be ; for greater density of 

 foliage generally, if not always, means that, owing to the superior 

 shade-enduring nature of the species in question, more of the buds 

 produced at the axils of the leaves have sprouted . than could have 

 continued their development if the species had been less shade- 

 enduring. Instances of the rule are deodar, silver fir, mango, 

 Buchanan/a latifolia, Eugenias, laurels, Terminalia tomentosa, 

 Diospyros Melanoxylon, Stephegyne parvlfolia, Mimusops mdica, 

 Pong ami a glabra, bamboos, the holly, Quercus incana, &c., &c. 

 Such species have obviously, irrespective of any other condition, 



