96 VERNATION OR PR^FOLIATIOX. 



(fig. 205 g), and called circinate (circino, I turn round); or folded later- 

 ally, conduplicate, as in Oak (fig. 205 b); or it lias several folds like a 

 fan, plicate or plaited, as in Vine and Sycamore (figs. 204/ 205 c), and 

 in leaves with radiating vernation, where the ribs mark the foldings ; 

 or it is rolled upon itself, convolute or supervolute, as in Banana and 

 Apricot (fig. 205 d) ; or its edges are rolled inwards, involute, as in 

 Violet (fig. 205 e); or outwards, revolute, as in Rosemary (fig. 205 /). 

 The different divisions of a cut leaf may be folded or rolled up separ- 

 ately, as in Ferns, while the entire leaf may have either the same or 

 a different kind of vernation. 



186. Other kinds of vernation receive their names from the arrange- 

 ment of the leaves in the bud, taken as a whole. Leaves in the 

 bud are opposite, alternate, or verticillate ; and thus different kinds of 

 vernation are produced. Sometimes they are nearly in a circle at 

 the same level, remaining flat, or only slightly convex externally, and 

 placed so as to touch each other by their edges ; thus giving rise to 

 valvate vernation (fig. 205 h). At other times they are at different 

 levels, and are applied over each other, so as to be imbricated, as in 

 Lilac, and in the outer scales of Sycamore (figs. 203, 204) ; and occa- 

 sionally the margin of one leaf overlaps that of another, while it, in its 

 turn, is overlapped by a third, so as to be twisted or spiral (fig. 205 i). 

 When the leaves are more completely folded, they either touch at their 

 extremities (fig. 205 &), or are folded inwards by their margin, and 

 become induplicate (fig. 205 1) ; or a conduplicate leaf covers another 

 similarly folded, while it covers a third, and thus the vernation is 

 equitant (riding), as in Privet (fig. 205 m) ; or conduplicate leaves are 

 placed, so that the half of the one covers the half of another, and thus 

 they become half-equitant or obvolute, as in Sage (fig 205 n). The 

 scales of a bud sometimes exhibit one kind of vernation, and the 

 leaves another (fig. 204). The same modes of arrangement occur in 

 the flower-buds, as will be afterwards shown. 



187. Leaf-buds, as has been stated, are either terminal or lateral. 

 By the production of the former (fig. 202 b t), stems increase in length, 

 while the latter (fig. 202 ba,ba,ba) give rise to branches, and add to 

 the diameter of the stem. The terminal leaf-bud, after producing 

 leaves, sometimes dies at the end of one season, and the whole plant, 

 as in annuals, perishes; or part of the axis is persistent, and remains for 

 two or more years, each of the leaves before its decay producing a 

 leaf-bud in its axil. This leat : bud continues the growth in spring. 



188. In some trees of warm climates, as Cycas, Papaw-tree, Palms, 

 and Tree ferns, the production of terminal buds is well seen. In these 

 plants, the elongation of the stem is generally regular and uniform, so 

 that the age of the plant may be estimated by its height. Such stems 

 (often endogenous) may thus be considered as formed by a series of 

 terminal buds, placed one over the other. From this mode of growth 



