352 MULTIPUOATION. 



CHAPTER II. 



MULTIPLICATION OF FOLIAR ORGANS. 



The cases refeiTible to tins head may be ranged 

 under two sections according as the increase is due to 

 phirality of ordinarily single organs, or to an increase 

 in the number of verticils or whorls. 



Wlien, in place of a single leaf organ two or more 

 are really or in appearance present the occurrence may 

 be due to one of several causes ; among them may be 

 mentioned an actual formation of parts in unwonted 

 number, hypertrophy or enation, chorisis or fission, 

 disjunction, adhesion of one leaf to another or to the 

 stem, as in some of the leaves called "geminate," 

 wherein the two leaves, though apparently in juxta- 

 position, yet originate from different parts of the stem, 

 but by coalescence or lack of separation produce the im- 

 pression as if they sprang from the same node. In the 

 adult state it is not always possible to ascertain with 

 certainty to which of these causes the increase in the 

 number of leaves is due, though a clue to the real state 

 of things may be gained from attention to the distribu- 

 tion of the veins, to the arrangement or phyllotaxy of 

 the leaves, the size and position of the supernumerary 

 organs, &c. 



The term "phyllomania," as ordinarily used, is applied 

 to an unwonted development of leafy tissue, as in some 

 begonias where the scales or ramenta are replaced by 

 small leaflets, or as in some cabbage leaves, from the 



of the sub-division of the leaf-like organs of Sciadopitys veiiicillata. In 

 one instance the pscudo leaf divided, and from the division proceeded a 

 little axis, bearing at its summit a verticil of pseudo leaves. This divi- 

 sion and formation of new axes and verticils affords ample confirmation 

 of the opinion thrown out by Professor Alexander Dickson, that the 

 apparent leaves of this plant were really branches : see ' Revne Horti- 

 cofe,' 1867, and ' Report. Bot. CongreBs.' London. 1866. p. 124. 



