12 THE STETTGGLE FOE EXISTENCE. 



extremes there is of course an infinitude of intermediate stages, but 

 for the purpose of this Manual it will be sufficient to assume that 

 where the difference of ages is only very slight, we have practically 

 the case of a crop composed of individuals of one and the same age, 

 and where it is at all appreciable, the consideration'of the instance 

 in question falls under the consideration of the larger case in which 

 the component plants are of every possible age. 



Hence it will be sufficient to consider separately the four follow- 

 ing cases, taking them in the order of their increasing complexity: — 



FiKST CASE. — That of a pure crop composed of individuals of one 

 and the same age. 



Second case — That of a pure crop composed of individuals of 

 all ages. 



Third case. — -That of a mixed crop composed of individuals of 

 one and the same age. 



FouKTH CASE. — That of a mixed crop composed of individuals of 

 all ages. 



SECTION I. 



FIRST CASE.— Pure crop composed of indiviuals of one and 

 the same age. 



In this case the crop may consist either entirely of seedlings, or en- 

 tirely of coppice-shoots, or of seedlingsand coppice-shoots combined. 



When the crop is composed exclusively of seedlings, as long as 

 these are small and stand apart, or possess only or chiefly the tap- 

 root, they do not impede the free development of their neighbours 

 either under or above ground, and the mutual struggle for existence 

 begins only when their crowns or roots have ramified and attained 

 sufficient lateral development to meet. 



But if coppice-shoots are present, the struggle obviously begins 

 with the very appearance of the crop. In the first place, the 

 several shoots of the same clump struggle with one another both 

 for air and hght and for the reserve materials stored up in the pa- 

 rent stools, roots or rhizomes; and, in the second place, as the 

 coppice-shoots begin to draw at onoe, from the moment they emerge 

 into the hght, crude nutrient materials through a more or les^- 

 extended root-apparatus, which is at first a portion of the root- 

 apparatus of the parent stool or plant itself, and afterwords au 



