Clare Island Survey — Phanerogamia. 10 63 



Transport by Wind. 



In the wind we have an agent which has been generally awarded 

 the premier place as a means of plant-dispersal. Ekstam, 1 discussing the 

 Spitzbergen and Nova Zembla floras, places the wind first as an agent of 

 seed- dissemination, the bird second, awarding to water a very subordinate 

 place ; and De Candolle remarks : " Le vent est la cause la plus generale et la 

 plus ordinaire de dissemination des especes sur toute la surface d'un pays." 2 



Many seeds have attached to them structures which render them especially 

 suited for distribution by means of the wind; yet, as has been observed by 

 many writers, this extreme ease of dispersal does not usually result in 

 wider or more thorough distribution. 



" In Compositae," says Bentham, 3 " several species of Eclipta, Mephantopus, 

 Anthemis, Zapsana, &c, without any pappus at all, have a much more wide- 

 spread distribution than the great majority of Senecios, for instance, with 

 their light seed and broad pappus." 



Or, to take a local example, Typha latifolia, which produces hundreds of 

 thousands of tiny seeds, with a higher capacity for remaining afloat in the air 

 than those of any other plume-seeded British species, is a less universal plant 

 in pools and streams than Sparganium ramosum, which bears in much 

 smaller numbers large and comparatively heavy seeds, quite incapable of 

 wind-dispersal (and generally considered to be spread by being eaten by 

 water-fowl). 



An exception is instanced by Bessey, 4 who finds, from a study of the Nevada 

 flora, that the plants with seeds suited for wind-dispersal are more widely 

 ■ distributed than those with fleshy or globular fruits, which are restricted in 

 their range. 



It is quite true, as Kronfeld 5 points out, that certain recent American 

 introductions, such as Erigeron canadense, Stenactis hellidiflora, and Galinsoga 

 parviflora, have rapidly achieved a wide dispersal in Europe by means of their 

 pappus-seeds; but other recent arrivals can be quoted, such as Matricaria 

 discoidea, which, without such means of dispersal, have spread equally fast. 



Nevertheless, there can be no doubt of the high efficacy of the wind in 

 dispersing seeds, though, as yet, we know little of the distance over which this 



1 0. Ekstam : he. cit., p. 59 ; and Eiuige bliitenbiologische Beobacbtungen auf Novaja Semlja. 

 Tromso Museums Aarsbefter, xviii, p. 191. 1897. 

 3 A. de Candolle, torn, cit., p. 613. 



3 G. Bentham : Anniversary Address, loo. cit., p. lxix. 



4 C. E. Bessey : Plant Migration Studies. University Studies, Univ. of Nebraska, v, pp. 1-27. 

 1905. 



6 M. Kronfeld : Studien iiber die Verbreitungsmittel der Pflanzen. Tbeil. 1. Windfriichtler. 

 Leipzig: Engelmann, 1900. Abstract in Justs Bot. Jabresbericht, xxix 2 (1901), pp. 637-8, 



