228 FLOWERS AND THEIR WORK. 



(Fig. 77). In such flowers the young and succulent ovaries 

 are exposed to various climatic influences, including strong 

 winds, intense sunlight, and rapid changes of temperature, 

 any of which may act injuriously upon the development of 

 the ovules, if the carpels are thin and freely exposed. There 

 is a tendency in most Flowering Plants to protect the ovary 

 from the influences mentioned above, and this tendency finds 

 expression in three distinct ways. 



OVARY 



RECEPTACLE! 



HYPOGYNOUS ! PERIGYNOUS EPIGYNOUS 



Fig. 77. Vertical Sections of Flowers, showing different forms of the Receptacle. 



(1) The petals tend to unite, as also do the sepals, thus 

 producing flowers of very specialised character (generally in 

 connexion with insect-pollination), in which the ovary is, at 

 the same time, protected to a certain extent from injurious 

 external influences. 



(2) The receptacle becomes more or less concave, and so 

 encloses and protects the carpel or carpels, leaving the stigma 

 exposed at the end of the style (e.g. Cherry, Rose). Such 

 flowers are said to be perigynous, but in many cases only 

 the marginal portion of the receptacle is concave or flattened, 

 so that the sepals and petals seem to have a common origin, 

 while the carpels arise from a prominence in the centre of the 

 flower (e.g. Blackberry). In perigynous flowers the pistil is 

 attached to the receptacle by its base only, and it is still said 

 to be superior even when the entire receptacle is concave and 

 only the stigmas project above it. 



(3) The receptacle grows around the ovary so that the 

 latter becomes completely embedded in it, the style and 



