164 On Plants and Insects. 



plant is not sticky, except just when this condition 

 is useful. All these viscous plants, as far as I 

 know, have upright or horizontal flowers. 



3. On the other hand, where the same object is 

 effected by slippery surfaces, the flowers are often 

 hanging ; creeping creatures being thus kept out of 

 them, just as the hanging 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 fer- 

 tilised by night-flying insects would derive no 

 advantage from being open in the day ; while, on 

 the other hand, those which are fertilised by bees 

 would gain nothing by being open at night. 



4. The Nottingham Catchfly (fig. 59) 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. The 

 upper part of the flowering stem is viscid, from 

 which it has derived its English name, the Notting- 

 ham Catchfly. This prevents the access of ants 

 and other small creeping insects. Each flower 

 lasts three days, or rather three nights. The sta- 

 mens are 10 in number, arranged in two sets, the 



