30 THE STEUGGIE FOE EXISTENCE. 



jury sustained by seedlings under overtopping trees is greater in di- 

 rect proportion to the depth, spread and density of the crowns of 

 these trees, since a deep, broad and dense crown means a proportion- 

 ately deep, close and wide spread of the roots and a proportionately 

 great absorptive power. (See also 2nd. paragraph of page 29). 



The preceding special remarks should be read in connection w^ith 

 all the observations of a more general character made under this 

 head in the First Case. 



VI. Individuax ages. — In the preceding Case, as it was essen- 

 tially based on the assumption that the crop was one consisting of 

 individuals of more or less one and the same age, we could consider 

 only the efPects of the advancing age of the entire crop. Here, al- 

 though no doubt each individual advances in age and the remarks 

 made in the First Case apply to it with httle or no modification, yet 

 the age of the entire crop considered as an individual body is a term 

 that is excluded by the very hj'pothesis of the case, and we have as 

 an effective substitute the condition which heads this paragraph. 



In the preceding paragraphs of this Case we have necessarily al- 

 ready considered trom most aspects the effect produced by a differ- 

 ence of individual ages. These it would be entirely superfluous to 

 repeat here. Only one principal point, and that of a totally general 

 nature, remains to be noticed. From the time that a seedling or 

 coppice-shoot makes its appearance, its vigour and tenacitv increase 

 in geometrical ratio until a few years after it has passed the phase of 

 maximum lateral development. Then a stationary period of more 

 or less short duration follows, succeeded by a dechne, at first very 

 gradual and afterwards increasing in geometrical ratio until death 

 supervenes. In this last phase, as already described on page 23, the 

 crown contracts and becomes spare, letting light pass through at va- 

 rious points, and the root-system contracts in proportion. Progres- 

 sively with this process the younger surviving neighbours, hitherto 

 overtopped or pressed in laterally, now make headway, and finally, 

 having acquired sufficient vigour, push up against and even into 

 and through their old rival, forcing it to contract still further its 

 diminished foKage and roots and ultimately hastening its death. 



VII. Relative longevity according to origin of lndivi- 

 DUALS.— All the remarks made under this head in the First Case 

 are to be accepted here in their fullest sense. It is thence evident 

 that seedling trees may be able to outhve much younger coppice- 

 shoots, especially if these stand on stools. Hence seedlings, once 

 they have attained a sufficiently large size, have notliing to fear 



