130 Flowers and their Unbidden Guests. 



and they fell inevitably either into the water or to the 

 ground. 



But of all flowers none present such difficulty of 

 access to small and wingless animals as do the pendulous. 

 No ant, for instance, ever getp inside the hanging 

 flowers of Oalanthus nivalis (Plate I. fig. 5). I may 

 therefore fairly infer that the nodding peduncles of small 

 pendulous flowers, as also the drooping axes of twining 

 plants, are developments that protect the nectar from 

 the unprofitable visits of creeping insects and thus 

 confer a benefit on the flowers. 



7. Temporary Suspension of the Fimctions of those Parts 

 of the Flower which attract Insects. 



The majority of those plants whose flowers only 

 open after sunset have a very short flowering period, 

 limited to a single night. A flower opens one evening, 

 remains open far into the night, or, perhaps, till dawn, 

 and then closes never to open again. Far rarer are 

 the species in which each flower repeats this evening 

 opening and this morning closure for several succes- 

 sive days. One of the best- known examples is Hesperis 

 tristis, a plant belonging to the Cruciferse; but the 

 family which presents by far the largest proportion of 

 species with flowers of this kind is the Caryophyllacese, 

 and as examples I may cite certain Sileneae, which I 



