144 THE LEAVES. 



leaves of the same bud in respect to each other. This last is evi- 

 dently connected with phyllotaxis, or their position and order of 

 succession on the stem. As to the first, leaves are for the most 

 part either bent or folded, or rolled up in vernation. Thus, the 

 upper part may be bent on the lower, so that the apex of the leaf 

 is brought down towards the base, as in the Tulip-tree, when the 

 leaves ai-e injlexed or recUnate in vernation ; or tlie leaf may be 

 folded along its midrib or axis, so that the right half and the left 

 half are applied together, as in the Oak and the Magnolia, when 

 the leaves are conduplicate ; or each leaf may be folded up a cer- 

 tain number of times hke a fan, as in the Maple, Currant, and Vine, 

 when they are said to be plicate or plaited. The leaf may be 

 rolled either parallel with its axis, or on its axis. In the latter case 

 it is spirally roUed up from the apex towards the base, hke a crosier, 

 or circinnate, as in true Ferns (Fig. 100), and among Phtenoga- 

 mous plants in the Drosera or Sundew. Of the former there are 

 three ways ; viz. the whole leaf may be laterally rolled up from one 

 edge into a coil, with the other edge exterior, when the leaves are 

 said to be convolute, as in the Apricot and Cherry ; or both edges 

 may be equally rolled towards the midrib ; either inwards, when 

 they are involute, as in the Violet and the Water-Lily ; or else out- 

 wards, when they are revolute, as in the Rosemary and Azalea. Fig. 

 214-219 are Linnsean diagrams of sections of leaves, illustrating 

 the princi]3al modes of vernation. 



258. Considered relatively to each other, leaves are valvate in 

 vernation when corresponding ones touch each other by their edges 



only, without overlap- 

 ping : they are imbri- 

 cated when the outer 

 successively overlap 

 the inner, by their 

 edges at least, in which 

 case the order of over- 

 lapping exhibits the 

 phyllotaxis, or order 

 of succession and po- 

 sition. In these cases 

 the leaves are plane or convex, or at least not much bent or rolled. 



FIG. 214. Conduplicate ; 215. Plicate or plaited ; 216. Convolute ; 217. Reyolute ; 213. 

 Involute ; and, 219. Circinate, vernation. 



