32 PART I. THE MORPHOLOGY OF PLANTS. [ 6. 



There may, however be no definite relation between the branches 

 and the leaves. For instance, the lateral branches of Lycopodium 

 are developed without any relation to the position of the leaves, 

 and in dichotomous branching no such relation can exist. 



When the shoot grows by means of a single apical cell, a direct 

 genetic relation can be traced between a branch and its correspond- 

 ing leaf. Thus, in Mosses, Equisetum, etc., the branch and the 

 leaf are both derived from the same segment of the apical cell. 



It does not necessarily follow, in those cases in which there is a 

 definite relation between leaf and branch, that every leaf has a 

 branch developed in relation with it, though this is frequently the 

 case. Floral and scaly leaves, for instance, have, as a rule, no buds 

 in their axils. 



It occasionally happens, in axillary branching, that more than 

 one bud is developed in the axil of a leaf. These buds may be ar- 

 ranged either one above the other (e.g. Aristolochia Sipho, Meni- 

 spermum canadense, Juglans regia in the axils of the cotyledons, 

 Honeysuckle, Gleditschia sinensis) in progressive succession, so 

 that the youngest is lowest in the axil ; or side by side (as inAllium 

 nigrmn, bulbs of Muscari botryoides, inflorescences of species of 

 Musa, among Monocotyledons ; and in some Willows, Poplars, and 

 Maples, among. Dicotyledons). In some cases, however (e.g. 

 Cuscufa), the presence of several buds in one axil is not due to in- 

 dependent development, but to the branching of a single original 

 bud. 



All the shoots that originate as lateral buds are not necessarily 

 developed into branches ; thus, in most trees, the buds which are 

 formed in the axils of the lowest leaves of the shoots of each year 

 usually remain undeveloped, and are only incited to growth when 

 the other buds are destroyed. Buds which thus remain unde- 

 veloped for along period, of ten for years, are called dormant, and 

 the shoots which are ultimately produced from them are said to be 

 deferred. 



6. Branch-Systems. The development from a parent 

 member of members similar to itself is termed branching, and it 

 frequently takes place in such a way as to lead to an aggregate 

 of similar members, constituting a branch-system. The morpho- 

 logical nature of the member does not determine the form of 

 branch-system to which it gives rise ; the leaf, the stem, the 

 root, the thallus, all present essentially the same types of branch- 

 svstems. 



