128 THE FACTORS [Part 



in allogamous flower-mechanisms (about lo %), as well as a much more considei 

 able increase in autogamy (about 15 %). 



The conditions of pollination in extreme arctic countries have bee- 

 investigated in Greenland by Warming. Insect-visits appeared to b 

 very rare. Anemophily and autogamy are correspondingly strongl} 

 and entomophily is weakly developed. Many flowers that are markedl 

 entomophilous elsewhere show a strong tendency to self-pollination ; fo 

 example, those of Mertensia maritima, the flowers of which are smalle 

 in Greenland than in Scandinavia, of Azalea procumbens, Vacciniur 

 Vitis-Idaea var. pumila, Bartsia alpina, Thj^mus Serpyllum, Menyanthe 

 trifoliata, Pyrola grandiflora. In spite of the scarcity of insects, th 

 allurements are not more strongly marked than when a rich insec 

 fauna exists, although this is contrary to an opinion that has bee 

 repeatedly expressed. 



Vegetative multiplication is strongly developed in Greenland, especially 1 

 plants in which self-pollination takes place with difficulty or to a slight exten! 

 ' In Greenland, which is poor in insects, the more entomophilous a species mf 

 be, the more it adapts itself to multiplication by vegetative means, where; 

 autogamous plants can dispense with this kind of propagation, and actually ( 

 dispense with it ' (Warming). 



The conditions of pollination have often been cited in explanation 

 the peculiarities o{ insular floras. Wallace, especially, has tried to conne 

 the presence, absence, or rarity of brightly coloured flowers on islanc 

 with the fauna. Thus on the islands of the eastern part of the Sou; 

 Pacific Ocean, for example in Tahiti, insects, especially Lepidoptera ai 

 bees, are rare : to this circumstance the poverty of the local flora 

 entomophilous flowers, especially in brightly coloured ones, and tl 

 prevalence of ferns have been ascribed. On the western islands, fl 

 example in Fiji, butterflies are more numerous and have produc- 

 through selection a greater number of brightly coloiu-ed flowers. T 

 flowers of the Galapagos have such inconspicuous flowers, that Darv. 

 could only after a long time convince himself that they nearly ■ 

 blossomed during his visit. As a matter of fact small Diptera a: 

 Hymenoptera are the only representatives of the insect-world on the 

 islands. 



Such tentative explanations are certainly interesting and suggestive ; b 

 yet it need hardly be stated, that the above peculiarities are explicable, r 

 merely by the conditions of pollination, but' by taking into considerati 

 also historical and climatic factors. Moreover, Wallace's views chie 

 rest on the incomplete information and collections of other biologi 

 •nvestigations scarcely lay in this direction, and thc\' have alrea 

 besrx refuted in many very important cases. Thus Wallace has describ^ 



