120 THE STORY OF PLANT LIFE 



bud, and regarded by some as bracteoles, which are 

 found, however, below them. The calyx is inferior 

 and persistent. The corolla is polypetalous and 

 hypogynous. 



There are five petals (or three or none), convolute, 

 overlapping to right or left, and the sepals do so in 

 the opposite direction. The petals are fugacious, 

 and broadly spreading. They turn towards the sun, 

 hence the name '' Sunflower," and close and open at 

 certain times. The stamens are indefinite, free, 

 hypogynous. They develop in descending order. 

 The pistil is syncarpous. There is a single ovary 

 and style, with three stigmas. The ovules are 

 numerous, or two in each carpel. The capsule is 

 one-celled, incompletely divided into several cells. 

 In Helianthemnm the capsule is three- valved. 



The flowers do not contain honey, and are visited 

 for pollen by many insects. The stamens are sensi- 

 tive in some cases, and the flower may open and close 

 by movements of the sepals. The anthers and stigma 

 ripen in some cases at different periods. 



The Rockroses are favourites in the garden. They 

 are of no other economic importance so far as the 

 British plants are concerned. 



Common Rock Rose [Helianthenmm vulgare). 



There are several plants whose flowers turn towards 

 the sun, by a process termed heliotropism, which is 

 the movement of a plant owing to the influence of 



