34 MANUAL OF BOTANY 



is developed at each point, and this becomes stronger than the one 

 from which it springs, we have a pseud-axis or sympodium formed, 

 closely resembling the sympodiimi of dichotomons branching. 

 It can be distinguished from the latter by the fact of the branch 

 arising behind the original growing point, and not from its 

 division. The sympodium may be helicoid or soorpioid as in 

 the other case. The branching of many forest trees is of this 

 kind. 



The pseud axis as first formed is crooked, and shows its 

 mode of formation (fig. 44, B, C). As it gets older the continued 

 growth and thickening of its successive parts cause it to become 

 straight {fig. 44, D), and it is then very difficult to distinguish it 

 from amonopodium, particularly when the leaves have fallen off. 



These modes of branching will be again alluded to under the 

 head of Infloeesobncb, in which their more practical application 

 arises. 



All lateral or axillary buds are called regular or normal, and 

 their arrangement in such cases is necessarily the same as that 

 of the leaves. As branches are formed from buds thus placed, 

 it should follow that their arrangement should also correspond 

 to that of the leaves. This corresponding symmetry, however, 

 between the arrangement of the branches and that of the leaves 

 is interfered with firom various causes. Thus, in the first place, 

 many of the regular buds may not be developed. Secondly, 

 other buds may arise irregularly at various other points than 

 the axils of leaves : these are called, from their abnormal origin, 

 adventitious. And, thirdly, accessory buds may be formed. 



1. N on -development of the Regular Buds. — This frequently 

 takes place irregularly, and is then altogether owing to local or 

 special causes ; thus, want of light, too much crowding, or bad 

 soil, may cause many buds to become abortive, or to perish after 

 having acquired a slight development. In other instances, how- 

 ever, this non-development of the buds takes place in the most 

 regiilar manner ; thus, in Firs, where the leaves are very closely 

 arranged in a spiral manner, the branches, instead of presenting 

 a siniilar arrangement, are placed in oh-cles around the axis at 

 distant intervals. This arises- from the non-development of 

 the buds of many of the leaves which form the spire, which is 

 followed by the development of those of closely succeeding leaves ; 

 and as such leaves are thickly placed, we are unable, after the 

 development of the branches, to trace clearl;\- the tm-ns of the 

 spire, so that the branches appear to be arranged in a circle. 



2. Adventitious Buds. — These have been found on various 



