78 THE STRUGGLE FOR EXISTKNCE. 



wise aborted leaves, and, to a greater extent than in coppicing, on 

 the formation of adventitious buds. 



XV. RELATIVE FACILITY OF THROWING UP ROOT-SUCKERS. 

 The faculty of producing root-suckers is limited to a comparatively 

 small number of trees, but those which possess it, have obviously 

 an enormous advantage over their companions. We already know 

 that suckers originate from adventitious buds, and that such buds, 

 although they may from anywhere on a young root, are produced 

 most abundantly and with greatest certainty along the edges of 

 wounds, and generally wherever the progress of the elaborated sap, 

 coming down from the crown, is arrested and there is a release of 



~ 



pressure. Thus standing trees bearing all their organs throw up 

 most suckers in soils of uneven texture (unevenness caused by pre- 

 sence of stones, &c.), in which the roots develop unequally, being 

 more vigorous at certain points than at others owing to better 

 oxgyenation and less impediment to their expansion. Moreover, 

 the faculty of throwing up suckers is always increased by any kind 

 of mutilation of the aerial portion oi the tree, being greater in 

 proportion to the extent of the mutilation, i. e. to the diminution of 

 other organs capable of carrying off the developmental energy of 

 the tree. Sufficient aeration is an absolute necessity for the for- 

 mation and subsequent development of adventitious buds on the 

 roots, for the buds could not be produced and begin to sprout with- 

 out the presence of oxygen. Hence suckers are always most abun- 

 dant in shallow or loose soils. Hence too the fact that in waterlogg- 

 ed soils trees reproduce themselves badly by means of suckers. This 

 also explains why, in tha irrigated plantation at Changa Manga, 

 the sissu fails to grow up again satisfactorily \vhen stubbed out. 



In Central India, Ougeinia dalbergioides forms large masses of 

 pure forest on land recently abandoned by cultivation, the husband- 

 ry operations having helped to multiply the number of suckers from 

 the original plants. The same, although to a much less degree, 

 may be said of the Diospyros Melanoxylon in the same forest re- 

 gion. One of the main causes ot the predominance of Boswellia 

 serrata in the dry forests of Central India is the facility with 

 which it throws up suckers. The gregariousness of sissu in North- 

 ern India is also in a gre.it measure due to the same cause, as is 

 also the invasive character of Buchanania latifolia in Northern and 

 Central India, and of Exccecaria selifera wherever it has been in- 

 troduced. 



It is evident that those trees and shrubs produce most suckers, 

 which *t>nd out long lateral roots that run along close under the 



