xxvm POLYNESIAN WEEDS 417 



culata and a species of Peperomia, both of them evidently growing 

 from seed dropped by birds. The fruits of Urena lobata and of 

 species of Sida, as well as those of Bidens pilosa and Ageratum 

 conyzoides, could be readily dispersed, entangled by their append- 

 ages in the plumage of birds, whilst the sticky achenes of Adeno- 

 stemma viscosum would easily adhere to feathers. Weeds with 

 drupes or berries like Geophila reniformis and Solanum oleraceum 

 would attract frugivorous birds, and I have often seen berries of the 

 last-named pecked by birds. Man has doubtless often been the 

 agent in dispersing the seeds of Leguminous weeds like Lablab 

 vulgaris. On the other hand, we know from the observations of 

 Focke (see page 150) that birds can distribute the seeds of a plant 

 like Vicia faba ; and in the Pacific islands it is evident from the 

 frequent occurrence of Tephrosia piscatoria on bare rocky hill tops 

 that its seeds are dispersed through the same agency. Birds also 

 probably carry about the seeds of Cardiospermum halicacabum. 



If we based our conclusion solely on the distribution of weeds 

 without a previous study of their means of dispersal we might, as 

 students of the distribution of man, acquire some startling and very 

 erroneous notions on the history of the races of man, especially in 

 the New World. Lacking such an acquaintance with existing 

 modes of dispersal it would not be prudent to attach too much 

 importance to the occurrence of Asiatic weeds in America and of 

 American weeds in Asia. Mr. Hemsley, in his work on the 

 botany of Central America (Biologia Centrali- Americana), gives a 

 list of ten British plants of world-wide range, which we will designate 

 plants of waste places rather than weeds. They are plants often 

 found not only in the Old and New Worlds, but also in the southern 

 hemisphere, and I will here name them : Radiola millegrana, 

 Alchemilla vulgaris, Cotyledon umbilicus, Lythrum salicaria, Con- 

 volvulus sepium, Sibthorpia europaea, Prunella vulgaris, Lycopus 

 europaeus, Aira caespitosa, Luzula campestris. According to this 

 authority these plants " are most unlikely to have been aided, 

 intentionally or unintentionally, by man " and " possess no special 

 means of dispersion by animals or birds or the elements " in the 

 way, as is implied, of appendages like hooks, hairs, a pappus, &c. 



Five of these plants are referred to in various connections 

 already in this work. In all I have tested the means of dispersal 

 of six or seven of them ; and although my results are not always 

 conclusive, I venture here to indicate some of them. The nutlets 

 of Prunella vulgaris and the seeds of Luzula campestris emit 

 mucus when wetted and adhere firmly to feathers on drying, 

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