36 ON PLANTS AND INSECTS. [LECT. 



Moreover, if larger flowers were visited by ants, not only 

 would these deprive the flowers of their honey, without 

 fulfilling any useful function in return, but they would 

 probably prevent the really useful visits of bees. If you 

 touch an ant with a needle or a bristle, she is almost 

 sure to seize it in her jaws ; and if bees, when visiting 

 any particular species, were liable to have the delicate tip 

 of their proboscis seized on by the horny jaws of an ant, we 

 may be sure that such a plant would soon be deserted. 



On the other hand, we know how fond ants are of 

 honey, and how zealously and unremittingly they search 

 for food. How is it, then, that they do not anticipate 

 the bees, and secure the honey for themselves ? Kerner 

 has recently published a most interesting memoir on this 

 subject, and has pointed out a number of ingenious con- 

 trivances by which flowers protect themselves from the 

 unwelcome visits of such intruders. The most frequent 

 are the interposition of chevaux de frise, which ants 

 cannot penetrate, glutinous parts which they cannot 

 traverse, slippery slopes which they cannot climb, or 

 barriers which close the way. 



Firstly, then, as regards chevaux de frise. In some 

 respects these are the most effectual protection, since 

 they exclude not only creeping insects, but also other 

 creatures, such as slugs. With this object, it will be 

 observed that the hairs which cover the stalks of so 

 many herbs usually point downwards. A good example 

 of this is afforded, for instance, by a plant, Knautia dip- 

 sacifolia (Fig. 31), allied to our common blue scabious. 

 The heads of the common carline (Carlina vulgaris) 

 (Fig. 33), again, present a sort of thicket, which must 

 offer an almost impenetrable barrier to ants. Some 



