SUMMARY. 



251 



nature, for simplification or reduction have played a 

 large role in the evolution of foliar organs ; the two 

 types of reversion met with are: (1) an increase in 

 complexity of the leaf, and (2) an increase in number 

 of the leaves ; Rejuvenescence of Foliage (of rever- 

 sionary nature). 



The phenomena of Simplification are much rarer 

 than those of Differentiation, for the changes involved 

 are mostly of progressive nature, i. e. in the direction 

 of evolution and not retrogressive. They include 

 Squamody of Foliage-leaves ; Pampinody of Foliage- 

 leaves ; Bracteody of Foliage-leaves ; Petalody of 

 Foliage-leaves ; Sporopbyllody of Foliage-leaves ; 

 Staminody of Foliage-leaves (probably reversionary) ; 

 •Carpellody of Foliage-leaves (possibly reversionary) ; 

 Bracteody of Scale-leaves ; Sepalody of Bracts ; 

 Staminody of Bracts ; Carpellody of Bracts ; Simpli- 

 fication of Foliage ; Fusion of Cotyledons ; Fusion of 

 Foliage-leaves ; Fusion of Scale-leaves ; Fusion of 

 Bracts; Suppression of Foliar Organs; filiations and 

 Ascidia of Foliage-leaves, comprising (a) Ascidia or 

 leaf-appendages, (b) Ascidia of the Entire Leaf, and 

 •(c) Laminar Enations ; these are regarded as, in a 

 sense, of reversionary nature; they probably repre- 

 sent (at least from one point of view) cases of incom- 

 plete facial fission of one leaf into two, or fusion of 

 two leaves into one, as the case may be, i. e. the 

 pitchers and enations of any given leaf are the 

 imperfect manifestation in a superficial position of 

 a second leaf. 



Under Adnation is described that of the Foliage- 

 leaf to Stem ; of Foliage-leaf or Bract to Peduncle ; 

 of Foliage-leaf to Perianth-leaf. All these, of course, 

 are progressive phenomena. 



Under Change of Position are described and dis- 

 cussed the subject of Leaf-arrangement (Phyllotaxis). 

 Cotyledons are first dealt with, and the phenomena of 

 Syncotyly and Schizocotyly, i. e. fusion and division 

 of cotyledons, described. As regards foliage-leaves 



