POLIAR ORGANS. Soo 
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 under 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 1s 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 leafletsin 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 


\ A \\ \A 

Fic. 183.—Supernumerary leaflet, Ulmus campestris. 
produced in the elm. In the one case the new leaflet 
springs from the apex of the petiole and partially fills 
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