FLOWERS AND THEIR WORK. 225 



both stamens and carpels, become petal-like ; in White Clover the 

 carpel sometimes remains open and produces green leaves on its 

 edges ; in Green Roses, double Cherry, etc., the carpels grow into 

 green, white, or coloured leaves. 



Examine and sketch (1) the entire pistil, (2) a cross-section of the 

 ovary, (3) a longitudinal section of the ovary, of each of the following 

 flowers : Narcissus, Tulip, Buttercup, Marsh Marigold, Wallflower, 

 Iris, Violet, Pansy, Mignonette, Dead-nettle, Foxglove, Snapdragon, 

 Cherry, Primrose, Stitchwort, Red Campion, Sweet William, 

 Mallow. 



256. Cohesion and Adhesion. "Fusion" between the 

 parts of the same or of different whorls is of common 

 occurrence. When the parts of the same whorl are united, 

 they are said to be coherent, but when union occurs between 

 the parts of different whorls, the term adherent is em- 

 ployed. 



Adhesion is not so common as cohesion, but in most 

 flowers which have a corolla-tube or perianth-tube the 

 filaments of the stamens are usually adherent to the tube, 

 so that the stamens appear to arise from corolla or perianth 

 instead of from the receptacle. Adhesion between stamens 

 and pistil occurs in Orchids and a few other plants. 



The apparent " fusion " of parts is really due to the 

 formation of a ring-like upgrowth of the receptacle, carrying 

 with it the free parts of the young flower, which thus appear 

 to have a common base. 



When the parts of the same whorl are free, the perianth is poly- 

 phyllous ; the calyx polysepalous ; the corolla polypetalous ; 

 the andrecium polyandrous ; the gynecium apocarpous. 



By cohesion (union between similar floral parts) the perianth 

 becomes gamophyllous ; the calyx gamosepalous ; the corolla 

 gamopetalous ; the andrecium mouadelphous (stamens united by 

 filaments, e.g. Mallow, Gorse), diadelphous (nine stamens united by 

 filaments, one free, in most Papilionaceae), polyadelphous (stamens 

 united by filaments into several bundles, e.g. St. John's Wort), or 

 syngenesious (stamens united by their anthers, e.g. Compositae) ; the 

 gynecium syucarpous (the styles or stigmas, or both, usually remain- 

 ing free). 



Adhesion (union between dissimilar parts) occurs only between 

 the stamens and other parts ; the stamens are epiphyllous 

 when united by their filaments to the perianth ; epipetalous when 

 so united to the corolla ; gynandrous when united to the style 

 (Orchids). 



8. B. 15 



