464 ZOOLOGICAL GEOGRAPHY. [part hi 



" New Zealand plants are remarkably scentless, both in regard to 

 the rarity of scented flowers, of leaves with immersed glands 

 containing essential oils, and of glandular hairs." There are a 

 few exceptional cases, but these seem even more rare than might 

 be expected, so that the confirmation of theory is very complete. 

 The circumstance that aromatic leaves are also very scarce, sug- 

 gests the idea that these, too, serve as an attraction to insects. 

 Aromatic plants abound most in arid countries, and on Alpine 

 heights ; both localities where winged insects are comparatively 

 scarce, and where it may be necessary to attract them in every 

 possible way. Dr. Hooker also informs, me that since his Intro- 

 duction to the New Zealand Flora was written, many plants with 

 handsome flowers have been discovered, especially among the 

 Raoiunculi, shrubby Veronicas, and herbaceous Composite. The 

 two former, however, are genera of wide range, which may have 

 originated in New Zealand by the introduction of plants with 

 handsome flowers, which the few indigenous insects would be 

 attracted by, and thus prevent the loss of their gay corollas ; so 

 that these discoveries will not much affect the general character 

 of the flora, and its very curious bearing on the past history of 

 the islands through the relations of flowers and insects. 



In judging of the relation here supposed to exist, it must be 

 remembered, that if the New Zealand insects have been intro- 

 duced from the surrounding countries by chance immigrations at 

 distant intervals, then, as we go back into the past the insect 

 fauna will become poorer and poorer, and still more inadequate 

 than at present to lead to the development of attractive flowers 

 and odours. This quite harmonizes with the fact of the ancient 

 indigenous flora being so remarkably scentless and inconspi- 

 cuous, while a few of the more recently introduced genera of 

 plants have retained their floral attractions. 



Concluding Remarks on the Early History of the Australian 



Region. 



We have already discussed in some detail, the various relations 

 of the Australian sub-regions to the surrounding Eegions, and the 

 geographical changes that appear to have taken place. A very 



