155 



Fig- 55- COMMON CARLINA (Carlina vulgaris). 



SECTION V.-ON PLANTS AND 

 INSECTS. 



I. 



I. IN the last chapter I endeavoured to show in 

 a variety of cases how beautifully flowers are con- 

 structed, so as to secure their fertilisation by insects. 

 Indeed, neither plants nor insects would be what 

 they are, but for the influence which each has 

 exercised on the other. Some plants, indeed, are 

 altogether dependent on insects for their very exis- 

 tence. We know now, for instance, that certain 

 plants produce no seeds at all, unless visited by 

 insects. Thus, in some of our colonies, the common 

 Red Clover sets no seeds on account of the absence 

 of humble bees ; for the proboscis of the hive bee 

 is not long enough to effect the object. According 

 to Mr. Belt, the same is the case, and for the same 

 reason, in Nicaragua, with the Scarlet-Runner. 



