GENERAL MOEPHOLOGY OF THE PLANT 89 



Violet and Water-lily, when it is involute ; 4th, the two 

 margins may be rolled outwards or towards the midrib on the 

 lower surface of the leaf (fig. 174), as in the Dock and Azalea, 

 in which case it is rrvolnte. 



We pass now to consider, secondly, the relation of the 

 several leaves of the same bud, taken as a whole, to one another. 

 Of this we have several varieties which may also be treated of 

 in two divisions: — 1st, those in which the component leaves are 

 fl,at ov slightly convex; and 2nd, where they are hent ov rolled. 

 Of the first division we may recognise three varieties : — 1st, that 

 in which the leaves are placed nearly in a circle or at the same 

 level, and in contact by their margins only, without overlapping 

 each other {fig. 176), when they are valvate ; 2nd, that in 



Fig. 169. Fig. 170. Fie. 171. Fig. 172. Fig. 173. 



Fig. 174. Fig. 175. 



Fig. 169. Vertical section of areclinate leaf. Fig. 170. Ti-ansTerse section 



of a oonduplicate leaf. Fig. 171. Transverse section of a plaited or pli- 

 cate leaf Fig. 172. Vertical section of a ciroinate leaf. Fig. 173. 



Transverse section of a convolute leaf. Fig. 174. Transverse section of 



a revolute leaf. Fig. 175. Transverse section of an involute leaf. 



which the leaves are placed at different levels, and the outer 

 successively overlap the inner to a greater or less extent by 

 their margins {fig. 177), as in the Lilac, and in the outer 

 scales of the Sycamore, when they are said to be imbricate ; 

 and 3rd, when leaves are placed as in imbricate vernation, and 

 one margin of each leaf overlaps that of another, while the other 

 margin, in its turn, is overlapped by a third {fig. 178), the verna- 

 tion is tivistecl or spiral. Of the second division, viz. where the 

 component leaves of the bud are hent or rolled, we have four 

 varieties : — 1st, when involute leaves are applied together in a 

 circle without overlapping {fig. 179), they are said to heindii- 

 plicate ; 2nd, when the leaves are conduplicate, and the outer 

 successively embrace and sit astride of those next within them. 



