40 ON PLANTS AND INSECTS. [lect. 



creeping creatures being thus kept out of them, just as 

 the pendulous nests of the weaver-bird are a protection 

 from snakes and other enemies. As instances of this 

 kind, I may mention the Common Snowdrop, and the 

 Cyclamen. 



Many flowers close their petals during rain, and this 

 is obviously an advantage, since it prevents the honey 

 and pollen from being spoilt or washed away. I have 

 elsewhere suggested that the so-called " sleep " of flowers 

 has reference to the habits of insects, on the ground 

 that flowers which are fertilized by night-flying insects 

 would derive no advantage from being open in the day ; 

 while, on the other hand, those which are fertilized by 

 bees would gain nothing by being open at night. I 

 confess that I suggested this' with much diffidence, but it 

 may now, I think, be regarded as well established. 



Silene nutans (Fig. 37), the Nottingham Catchfly, is a 



very instructive species from this point of view, and 



indeed illustrates a number of 



interesting points in the relations 



between plants and insects. Its 



life history has recently been well 



described by Kerner. The upper 



part of the flowering stem is 



viscid ; from which it has derived 



Fig. si.— silene nutans. its English name, the Nottingham 



Catchfly. This prevents the access 



of ants and other small creeping insects. Each flower 



lasts three days, or rather three nights. The stamens 



are ten in number, arranged in two sets, the one set 



standing in front of the sepals, the other in front 



