74 MORPHOLOGY, OK COMPARATIVE ANATOMY. 



midrib and the lateral halves are placed face to face (Oak) ; and 

 plicate (fig. 129), where the blade exhibits several perpendicular 

 folds, as in a fan (Vine, Beech, Maple, Currant, &c.) ; this last is 

 often combined with the preceding. "When rolled up, also, the 

 rolling may take place in either direction : where the apex of the 

 leaf is rolled down toward the base, as in the Ferns and in the 

 flower-stalk of Drosera, it is circinate ; if the leaf is rolled up from 

 side to side like a plan, with only one edge free, as in the Cherry 

 &c., it is convolute (fig. 130) ; when both margins are rolled inward 

 toward the midrib, it is involute (fig. 127) ; and when both margins 

 are rolled outward toward the midrib, it is revolute (fig. 131). 



Sect. 6. THE INFLORESCENCE. 



In all Flowering Plants, a portion of the buds change their 

 character at certain periods and in certain situations. They cease 

 to elongate and produce true leaves, while the foliaceous organs of 

 which they are composed are gradually developed into that assem- 

 blage of organs which constitutes a flower. 



So intimately are the leaf-hud and flower-bud related, that, under 

 peculiar conditions, producing monstrous growths, flower-buds are seen 

 to expand into tufts of green leaves, or imperfect flowers to throw out 

 leafy shoots from their centres ; such cases are often observed, for instance, 

 in cultivated Roses ; and leaf-shoots may likewise exhibit more or less of 

 the characteristics of a flower, &c. 



Flower-buds are subject to the same laws of arrangement as 

 leaf-buds. The buds which commence the growth of the repro- 

 ductive structures may be at once developed into solitary flowers, 

 or, as is more common, the blossom-buds unfold into a system of 

 branches terminating in flowers, the branches all originating in the 

 axils of modified leaves, called bracts. The solitary flower, or the 

 connected system of flowers arising from one point, is called the 

 inflorescence, which is either terminal or axillary. 



The inflorescence is produced from the terminal bud, or from this and 

 one or more of the upper axillary buds, in most annual plants ; and there 

 is often a gradual transition from the true-leaf stem into the bract-region, 

 or inflorescence. The same is the case, to a great extent, with the 

 flowering stems of biennials. The inflorescence of herbaceous perennials, 

 bulbs, &c. is either terminal or axillary, as is that of arborescent plants. 

 In the Horse-chestnut (tig. 123) and Lilac, for example, the terminal 

 bud usually ends in a blossom, while in the Apple and its allies the inflo- 

 rescence is axillary. 



When the inflorescence is developed from the terminal bud of an un- 

 branched stem, the growth of the plant ends in the blossoming, as is the 



