62 MANUAL OF BOTANY 



leaf indeed may be traced to its behaviour in this respect. It 

 differs from the stem in the degree to which its branching may 

 be carried, seldom showing branches of more than the second 

 or third order. 



The part of the stem or branch from which a leaf arises is 

 called a, node, and the space between two nodes an iniemode. 

 The portion of the leaf next the stem is termed the hose, the 

 opposite extremity the apex, and the lines connecting the base 

 and apex the margins. The leaf, being commonly of a flattened 

 nature, has only two surfaces ; but when succulent it has 

 frequently more than two. The terms upper and lower are 

 applied to the two surfaces of ordinary leaves, because in by far 

 the greater number of plants such leaves areplaced horizontally, 

 so that one surface is turned upwards, and the other downwards. 

 There are certain leaves, however, which are placed vertically, 

 as those of some species of Eucalyptus, in which case the 

 margins are turned upwards and downwards instead of the 

 surfaces. The angle formed by the union of the upper surface 

 of the leaf with the stem is called the axil, and everything 

 which arises out of that point is said to be axillary to the 

 leaf; if anything springs from the stem above, or below the 

 axil, it is extra-axillary ; or, as more generally described when 

 above, supra-axillary ; when below, infra-axillary . 



Duration and Fall of the Leaf. — The leaf varies as regards 

 its duration, and receives different names accordingly. Thus, 

 when it falls off soon after its appearance, it is said to be 

 fugacious or caducous ; if it lasts throughout the season in 

 which it is developed, it is deciduous or annual ; or if beyond 

 a single season, or until new leaves are developed, so that the 

 plant is never without leaves, it is persistent, evergreen, or 

 perennial. 



The parts of the leaf. — The axis of the leaf may be termed 

 3. phyllopodium; it is capable of very varied development, and 

 its region of active growth is seldom altogether apical as in the 

 stem axis. It commences apically, but this apical growth is 

 usually superseded by a basal growth, which continues after the 

 former has ceased. This is especially well seen in the long 

 narrow leaves of many Monocotyledons. 



In the phyllopodium three regions may be distinguished. 

 The so-called leaf-hase, or hypopodium, including that region 

 which is attached to the stem ; the lamina, or epipodiimi, which 

 is the usually flattened terminal portion, which forms what is 

 often alluded to generally as the leaf proper ; and an inter- 



