INSULAR PLANTS AND INSECTS. 277 



combination with their colours, as an attraction to insects, 

 it might be anticipated that where colour was deficient 

 scent would be so also. On applying to my friend Sir 

 Joseph Hooker for information as to the odoriferous 

 qualities of New-Zealand plants, he informed me, that 

 the New-Zealand flora is, speaking generally, as strik- 

 ingly deficient in sweet odours as it is in conspicuous 

 colours. Whether this peculiarity occurs in other islands 

 I have not been able to obtain information ; but we may 

 certainly expect to find it where colour is so strikingly 

 deficient as in the flora of the Galapagos Islands. 



Another question which here comes before us, is the 

 origin and meaning of the odoriferous glands of leaves. 

 Sir Joseph Hooker informed me that not only are New- 

 Zealand plants deficient in bright coloured and sweet- 

 smelling flowers, but equally so in scented leaves. This 

 led me to think that perhaps such leaves were in some 

 way an additional attraction to insects though it is not 

 easy to understand how this could be, except by adding 

 a general attraction to the special attraction of the 

 flowers, or by supporting the larvae which, as perfect in- 

 sects, aid in fertilization. Mr. Darwin, however, informs 

 me that he considers that leaf-glands bearing essential oils 

 are a protection against the attacks of insects where these 

 abound, and would thus not be required in countries 

 where insects were very scarce. But it seems opposed 

 to this view that highly aromatic plants are charac- 

 teristic of deserts all over the world, and in such places 

 insects are not abundant. Mr. Stainton informs me that 

 the aromatic Labiatse enjoy no immunity from insect 

 attacks. The bitter leaves of the cherry-laurel are often 

 eaten by the larvre of moths that abound on our fruit- 



