[172] Report of the Brit. Assoc. Committee on Migration of Birds during 1886.
[173] Trans. Ent. Soc., 1871, p. 184.
[174] Nature (1875), vol. xii. pp. 279, 298.
[175] I am indebted to Professor R. Meldola of the Finsbury Technical Institute, and Rev. T.D. Titmas of Charterhouse for furnishing me with the weights required.
[176] See Nature, vol. vi. p. 164, for a summary of Kerner's paper.
[177] It seems quite possible that the absence of pappus in this case is a recent adaptation, and that it has been brought about by causes similar to those which have reduced or aborted the wings of insects in oceanic islands. For when a plant has once reached one of the storm-swept islands of the southern ocean, the pappus will be injurious for the same reason that the wings of insects are injurious, since it will lead to the seeds being blown out to sea and destroyed. The seeds which are heaviest and have least pappus will have the best chance of falling on the ground and remaining there to germinate, and this process of selection might rapidly lead to the entire disappearance of the pappus.
[178] See Island Life, p. 251.
[179] Mr. Hemsley suggests that it is not so much the difficulty of transmission by floating, as the bad conditions the seeds are usually exposed to when they reach land. Many, even if they germinate, are destroyed by the waves, as Burchell noticed at St. Helena; while even a flat and sheltered shore would be an unsuitable position for many inland plants. Air-borne seeds, on the other hand, may be carried far inland, and so scattered that some of them are likely to reach suitable stations.
[180] For fuller particulars, see Sir J. Hooker's Introduction to Floras of New Zealand and Australia, and a summary in my Island Life, chaps. xxii. xxiii.
[181] For a fuller discussion of this subject, see my Island Life, chap. xxiii.