FLOWERS AND THEIR WORK. 227 



259. The Floral Formula. As a means of readily and 

 rapidly indicating the essential features in the structure of a 

 flower, what are known as floral formulae are frequently 

 employed, and these, together with the diagram and vertical 

 (longitudinal) section (with the parts labelled), will repre- 

 sent all the essential features in the structure of the flower 

 without a word of description being necessary. 



The symbols and f respectively denote radially and 

 bilaterally symmetrical (zygomorphic) flowers. The signs 

 <, ? v 9 respectively denote staminate, carpellary, and 

 hermaphrodite (" perfect ") flowers. The letters K, C, or P 

 represent the calyx and corolla (or perianth), A and G- the 

 andrecium (stamens) and gynecium (pistil), and the figure 

 following each letter gives the number of parts in each series. 

 Cohesion is indicated by brackets enclosing the number of 

 parts ; a horizontal bracket ^ indicates adhesion between the 

 parts of successive whorls ; a horizontal line above GT means 

 that the ovary is inferior, a line below G- that it is superior ; 

 the symbol oo is used when there are numerous parts in any 

 series. The following are examples of floral formulas : 



Buttercup K5, 05, Aoo , GOK 



Narcissus P(3 + 3),A3 + 3, G (3). 



Violet fK5, G5, A5, G (3). 



Dead-nettle t K(5), C(5), A4, G (2). 



Stitchwort K5, C5, A5 + 5, G (3). 



Draw the floral diagram and write the floral formula of the follow- 

 ing flowers : Lesser Celandine, Marsh Marigold, Larkspur, Broad 

 Bean, Gorse, Tulip, Iris, Early Purple Orchid, White Dead-nettle, 

 Foxglove, Sweet William, Primrose, Wallflower. 



26O. Ferigyny and Epigyny. The shape of the re- 

 ceptacle or thalamus varies very much in different flowers. 

 The receptacle of the Buttercup is convex, and the successive 

 cycles of floral parts are placed upon it, one above the other, 

 the sepals arising first and the carpels last. Flowers of this 

 type are said to be hypogynous, and the pistil superior 



