ORGANS OF NUTRITION. 



145 



be rolled up from one margin into a single coil, with the other 

 margin exterior, as in the Apricot, Cherry, and Plantain, in 

 which case it is convolute (Jig. 274); 3rd, the two margins of the 

 leaf may both be rolled inwards towards the midrib, which re- 

 mains immoveable, as in the Violet, and Water-Lily (^^r. 275), 

 when it is involute; or 4th, the two margins may be rolled out- 

 wards or towards the lower surface of the leaf, as in the Rose- 

 mary, Lavender, and Azalea (fiy. 276), in which case it is 

 revolute. 



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

 leaves of the same bud taken as a whole, to each other. Of this 

 vernation we have several varieties which may be treated of 

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

 are plane or slightly convex ; and 2nd, Where they are bent 

 or rolled. Of the first division we shall describe three varie- 

 ties:— 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 one another (Jig. 277), Avhen they 

 are valvate ; 2nd, when they are at different levels, and the 

 outer successively overlap the inner to a greater or less ex- 

 tent by their margins, as in the Lilac, and in the outer scales 

 of the Sycamore (Jig. 278), when they are said to be imbri- 

 cate ; or 3rd, if when leaves are placed, as in imbricate verna- 

 tion, the margin of one leaf overlaps that of another, while it, 



Fig. 278. 



Fig. 279. 



Fig. 281. Fig. 282. Fig. 283. 



Fig. 277. Transverse section of a bud to show the leaves arranged in a valvate 



manner. 

 Fig. 278. Transverse section of a bud to show imbricate vernation. 

 Fig. 279. Transverse section of a bud to show twisted or spiral vernation. 

 Fig. 280. Transverse section of a bud to show induplicate vernation. 

 Fig. 281. Transverse section of a bud showing equitant vernation. 

 Fig. 282. Transverse section of a bud showing obvolute vernation. 

 Fig. 283. Transverse section of a bud showing supervolute vernation. 



in its turn, is overlapped by a third (Jig. 279), the vernation is 

 twisted or spiral. We have now to describe the varieties of the 

 second division, viz. where the component leaves of the bud are 



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