DIV. i MORPHOLOGY 125 



so that the resulting shoots are regularly arranged at similar distances from one 

 another both longitudinally and laterally. 



The habit of the branch-system depends on the distribution of the expanding 

 buds, whether this is alternate or in whorls. When the buds are opposite a kind 

 of dichotomous branching results as in the Horse Chestnut or the Elder. 



4. DIRECTION AND INTENSITY OF GROWTH OF THE LATERAL 

 BRANCHES in relation to one another. The lateral angle between 

 adjacent lateral branches on an orthotropous branch may be very 

 constant in any kind of plant (e.g. in Araucaria or Pinus). On the 

 other hand, the intensity of growth of the lateral axes on the same main 

 axis may show much variety. Frequently, with the appearance of a 

 division of labour, only some of the branches are of unlimited growth, 

 the others forming short shoots. The latter have usually a shorter 

 life, tend not to branch, and do not take part in the persistent branch- 

 system of the tree. In the Larch, for example, the short shoots form 

 short rosettes of needles on the older shoots of unlimited growth. 



5. DIRECTION AND INTENSITY OF GROWTH OF THE LATERAL 

 BRANCHES IN RELATION TO THE MAIN Axis. DIFFERENT TYPES OF 

 LATERAL BRANCHING. The angle at which the lateral branch is 

 inclined to its main axis also tends to be very constant in any species 

 (e.g. Pine). 



The lateral branches may grow at the same rate as the parent 

 axis, or less rapidly, or much more rapidly. In the last case they 

 take precedence of the main axis, the growth of which may cease 

 entirely, while one or more lateral branches take over the continuance 

 of the branching. Diversity in the resulting branch -systems must 

 evidently result from such differences in the growth of the daughter 

 and parent axes. This has led to the distinction of various types 

 of lateral branching, a knowledge of which is indispensable to the 

 understanding of the morphological construction of the higher plants. 

 The differences are especially well seen when the branches are close, 

 as in the region where the reproductive organs or flowers are borne 

 as lateral branches. The INFLORESCENCES may therefore serve as 

 favourable examples of the different types of branching. 



The bracts and bracteoles in the inflorescence are usually developed as scale 

 leaves and do not resemble the foliage leaves. They do not serve for assimilation 

 but only for the protection of the young lateral branches in their axils. If the 

 branching of a lateral branch is continued, this proceeds as a rule from the axils of 

 the bracteoles. It is further characteristic of many inflorescences that the axillary 

 buds of all the bracts are developed further. Owing to this the inflorescences, 

 in contrast to the vegetative shoot-systems, form crowded branch-systems, very 

 numerous flowers being formed in a small space. 



(ft) The term racemose branching is applied when the main axis 

 grows MORE ACTIVELY than the lateral axes of the first order, and 

 these in turn more actively than the branches of the second order 

 arising on them ; also when the main axis grows as actively as its 



