INDUSTRIAL PKOGRESS DURING THE YEAR 1876. cxlv 



Science, was on the contributions made to the theory of Evolution 

 by American naturalists. 



In his late address before the section of Biology of the British As- 

 sociation, Mr. Alfred R. Wallace remarked on the peculiar relations 

 of plants and insects as exhibited on islands. As many plants can 

 only be fertilized by insects, the absence of the latter would, of 

 course, tend to prevent the continued existence of jDlants. This af- 

 fords a clew to much of the peculiarity of the floras of oceanic isl- 

 ands. Albatrosses, gulls, puffins, tropic birds, and many others nest 

 inland, often amid dense vegetation ; and it is thought that they 

 often carry seeds, attached to their feathers, from island to island, 

 for great distances. In the tropics they often nest on the mountains, 

 far inland, and may thus aid in tlie distribution even of mountain 

 plants. Insects, on the other hand, are mostly conveyed by currents 

 of air, especially by violent gales ; and it may thus often happen 

 that totally unrelated plants and insects may be brought together, 

 in which case the former must often perish for want of suitable in- 

 sects to fertilize them. Much of the poverty and exceptional distri- 

 bution of the plants of the Polynesian Islands is probably due to 

 the great scarcity of flower-frequenting insects. Lepidoptera and 

 Hymenoptera are exceedingly scarce in the eastern islands of the 

 Pacific, and it is almost certain tliat many plants which require 

 these insects for their fertilization have been thereby prevented 

 from establishing themselves. In the western islands, such as the 

 Fijis, several species of butterflies occur in tolerable abundance, and 

 no doubt some flower-haunting Hymenoj^tera accompany them ; 

 and in these islands the flora appears to be much more varied, and 

 especially to be characterized by a much greater variety of showy 

 flowers. Mr. Moseley has suggested that a flower which had acquired 

 a brilliant color to attract insects might, on transference to another 

 country, and becoming so modified as to be capable of self-fertiliza- 

 tion, retain the colored petals for an indefinite period. Such is 

 probably the explanation of the pelargonium of Kergueleu's Land, 

 which forms masses of bright color near the shore during the flower- 

 ing season, while most of the other plants of the island have color- 

 less flowers, in accordance with the almost total absence of winged 

 insects. " The researches of Dr. Herman Miiller have shown us by 

 what minute modification of structure or of function many flowers 

 are adapted for partial insect- and self-fertilization in varying de- 

 grees ; so that we have no difficulty in understanding how, as the 

 insects diminished and finally disappeared, self-fertilization may 

 have become the rule, while the large and showy corollas remain to 

 tell us plainly of a once different state of things." 



A new work, by Mr. Alfred R. Wallace, on the geographical dis- 

 tribution of animals, bids fair to prove of much interest to natural- 

 ists, though it will aflbrd food for discussion. 



7 



