FOLIAU ORGANS. 



363 



surface of which project, at right angles to the primary 

 plane, other secondary leafy plates; but these are, 

 strictly speaking, cases of hypertrophy (see Hyper- 

 trophy). 



Those instances in which the actual number of leaves 

 is increased, so that in place of one there are more 

 leaflets, may be included imder the term "pleiophylly," 

 which may serve to designate both the appearance of 

 two or more leaves in the place usually occupied by a 

 single one, and also those normally compound leaves 

 in which the number of leaflets is greater than usual. 



The increased number of leaves in a whorl may well 

 be designated as " polyphylly," using the word in the 

 same sense as in ordinary descriptive botany, while 

 " pleiotaxy" may be applied to those cases in which 

 the number of whorls is increased. 



Pleiophylly. As above stated, this term is proposed to 

 designate those cases in which there is an absolute 

 increase in the number of leaves starting from one 

 particular point, as well as those in which the number 

 of leaflets in a compound leaf is preternaturally increased. 

 The simplest cases are such as are figured in the 

 adjacent cuts, wherein, in place of a single leaf, two are 



Fio. 183. Supernumerary leaflet, Ulimia eampestris. 



produced in the elm. In the one case the new leaflet 

 springs from the apex of the petiole and partiallv fills 



23 



