xv THE DEVELOPMENT OF THE FLOWER 195 



stomata, and between the upper and lower epidermis comes the 

 mesophyll, which is penetrated and strengthened with vascular 

 strands. 



The Texture of the Sepals. The texture of sepals varies con- 

 siderably. They may be delicate, firm, membranous, or scaly. 

 The duration of the sepals will depend upon their texture. They 

 may fall off when the flower opens, when they are said to be 

 caducous; if they last until the seeds begin to ripen and then 

 fall off, they are deciduous ; and when they remain until the seeds 

 are ripe, they are persistent. The surface of the sepals is fre- 

 quently provided with hairs for protection. 



Functions of the Sepals. When the sepals are green they 

 perform the same functions as foliage leaves. They also serve 

 to protect the other floral leaves from injury. If they are petaloid 

 they may serve to attract insects, as in the Anemone and 

 Lilies. 



The Structure and Functions of the Petals. The 

 petals and petaloid sepals are covered with a delicate epidermis. 

 Within the epidermis come one or more layers of spongy paren- 

 chyma ; this is traversed with a number of delicate vascular 

 strands, which, as in foliage leaves, gives it a veined appearance. 



The Texture of the Petals. The texture of the petals is 

 usually delicate. They are deciduous, z>., they fall off as the 

 seeds ripen. The surface of the corolla may be smooth or 

 glabrous (p. 29), or present certain hair structures or hair-like 

 outgrowths. 



The Colour of Petals and Sepals. When the sepals and (less 

 often) the petals are green, the colour is due to chlorophyll. 

 The petals are, however, as a rule coloured, the colour being 

 due either to coloured sap or to chromoplasts (p. 84). In a 

 few cases the colouring is due to both. 



The Functions of the Petals. The colour, markings, shape, 

 and perfume of the corolla are all designed to attract insects, 

 so as to ensure the distribution of the pollen (p. 198). The 

 petals also protect the essential organs (stamens and pistil) of 

 the flower from injury. Petals may be modified to form nectaries 

 or glands for the preparation of honey. Petals thus have a two- 

 fold function, attractive aud protective. 



EXPT. 175. From a flower of the Geranium strip off a petal, and with 

 a sharp knife pull away the surface tissue. Mount the petal in water 



2 



