The geographical distribution of animals, with a study of the relations ...

464 ZOOLOGICAL GEOGRAPHY. [part hi" New Zealand plants are remarkably scentless, both in regard tothe rarity of scented flowers, of leaves with immersed glandscontaining essential oils, and of glandular hairs." There are afew exceptional cases, but these seem even more rare than mightbe expected, so that the confirmation of theory is very complete.The circumstance that aromatic leaves are also very scarce, suggeststhe idea that these, too, serve as an attraction to insects.Aromatic plants abound most in arid countries, and on Alpineheights ; both localities where winged insects are comparativelyscarce, and where it may be necessary to attract them in everypossible way.Dr. Hooker also informs, me that since his Introductionto the New Zealand Flora was written, many plants withhandsome flowers have been discovered, especially among theRaoiunculi, shrubby Veronicas, and herbaceous Composite. Thetwo former, however, are genera of wide range, which may haveoriginated in New Zealand by the introduction of plants withhandsome flowers, which the few indigenous insects would beattracted by, and thus prevent the loss of their gay corollas ; sothat these discoveries will not much affect the general characterof the flora, and its very curious bearing on the past history ofthe islands through the relations of flowers and insects.In judging of the relationhere supposed to exist, it must beremembered, that if the New Zealand insects have been introducedfrom the surrounding countries by chance immigrations atdistant intervals, then, as we go back into the past the insectfauna will become poorer and poorer, and still more inadequatethan at present to lead to the development of attractive flowersand odours.This quite harmonizes with the fact of the ancientindigenous flora being so remarkably scentless and inconspicuous,while a few of the more recently introduced genera ofplants have retained their floral attractions.Concluding Remarks on the Early History of the AustralianRegion.We have already discussed in some detail, the various relationsof the Australian sub-regions to the surrounding Eegions, and thegeographical changes that appear to have taken place. A very