THE ANGIOSPERMAE 



1 155 



example, may often act in the same way as the petals do in other cases, while 

 a great many flowers ensure that the pollen shall not be washed away by 

 rain and lost, through the bending of the pedicel which turns the flowers 

 downwards in darkness or in rainy weather. Protection from robbery by 

 small insects concerns the nectar more than the pollen and as a means to this 

 end the flower is sometimes permanently closed to all but large and strong 

 insects, or else the corolla is so narrowed and elongated that only long- 

 tongued insects can reach it. A well-known example of the closed flower is 

 the type known as personate, of which the garden Antirrhinum is a con- 

 spicuous case (Fig. 1 128). The two lower petals of the tubular corolla are 

 so humped that they fill the mouth of the tube. They are hinged at the 

 sides, however, so that a humble bee, clasping the flower between its legs, 



Fig. 1 128. — Antirrhinum majiis. Flower with personate 



corolla. 



can force the obstructive petals to bend downwards, opening the mouth 

 of the flower for the entrance of its tongue. The common name of Snap- 

 dragon is derived from this opening and shutting of the mouth of the flower 

 when it is gently squeezed. 



We have already spoken of the symmetry of the perianth in a previous 

 section of this chapter, but there are one or two cases deserving another 

 mention here, in which zygomorphic symmetry is related to the special 

 functions of the perianth in anthesis. One such case is the frequent occur- 

 rence of asymmetric perianths, especially corollas, in flowers at the periphery 

 of a closely-massed inflorescence, in which the petals standing radially 

 outwards are bigger than those directed radially inwards (cf. Exotrophy, 

 p. 1 1 14). This type of zygomorphy is quite diflrerent from that in, for 

 example, a Viola, for it is not related to pollination of the individual flower. 

 Moreover these flowers, like their radially symmetrical neighbours, are 



