40 PAKT I. THE MORPHOLOGY OF PLANTS. [ 10- 



and, in other cases, independently of the development of repro- 

 ductive organs, as in Hyhcomium splendens, a pleurocarpous Moss, 

 the shoots of which grow for but one year; and in the seedlings 

 of the Lime, and of the Elm, which form no terminal bud at 

 the close of the first year, the further development of the shoot 

 being effected by the highest lateral bud. 



In those shoots of trees which are produced in one season's growth, the lowest 

 internodes, especially those lying between the bud-scales, are very short ; so that 

 it is easy, by noticing the closely-arranged scars of the bud-scales, to deter- 

 mine, in a shoot several years old, the amount of growth during each year. 

 The terminal and the lateral buds of such an annual shoot usually remain in 

 the bud-condition during the first year until the beginning of the next 

 period of growth, so that the age of such a branch-system can be determined 

 by the extent of the branching, the number of years corresponding to the 

 number of times that branching has taken place. In some trees, however, (e.g. 

 the Oak) a second shoot, which had hitherto existed in the bud-condition, is 

 regularly developed in the middle of summer. As a general rule, it is only the 

 more anterior (near the apex) of the lateral buds on the shoot which develope 

 in the subsequent year into branches, as is very clearly seen in the whorled 

 branches of the Coniferae ; when, however, the more posterior lateral buds do 

 develope, the branches produced are successively the shorter the further they 

 are from the apex (e.g. Elm). Whilst in many trees (Conifers, Oak) the 

 terminal bud of a shoot always grows into a new shoot in the next year, in others 

 (Lime, Elm, sometimes Beech) this is not the case, but the elongation of the 

 shoot is effected in a sympodial manner by means of the highest lateral bud 

 (see p. 35). 



In the Larch, the dwarf-shoots bear the fascicled leaves, and spring from the 

 axils of the leaves of an ordinary shoot of the same year ; they usually elongate 

 but slightly each year, but they may, under certain circumstances, develope 

 into ordinary shoots. In the Scots Pine, the dwarf-shoots bear only two green 

 leaves, in addition to scaly leaves ; they arise in the axils of the leaves of the 

 ordinary shoots of the same year, and they fall off when the leaves die. In 

 dicotyledonous trees, these dwarf-shoots occur especially in advanced age, or 

 when the growth of the tree is stunted. They are very conspicuous in the 

 Apple, Pear, and other similar trees, and are the only parts of the tree which 

 produce flowers and fruit. 



The Bulb and the Corm are examples of shoots with short stems ; they are, 

 in fact, forms of the bud, produced underground. 



The Bulb consist of a flattened discoid stem (Fig. 22 B), bearing a number of 

 scaly leaves closely arranged on its upper surface, and roots on its lower surface. 

 The leaves may either invest each other, as in the Onion, when the bulb is said 

 to be tunicate ; or they may overlap at their edges, as in the Lily, when the 

 bulb is said to be imbricate. 



Aerial buds develope in some plants into small bulbs, termed bulbils, as in 

 Liliuni bulbiferum, Dentaria bulbifera, and in some species of Onion. 



The Corm consists of a rounded or flattened stem which occupies a relatively 



