10 80 Proceedings of the Royal Irish Academy. 



a lucky preponderance of upward gusts over downward ones if it is to cross 

 the channel safely. It will be only one seed out of a large number which will 

 in all probability encounter such good fortune. But if tens of thousands of 

 seeds are given such a chance occasionally during tens of thousands of years, 

 a probability of colonization may be granted by the most severe critic. The 

 high efficiency of this seed for wind-dispersal is the outstanding constant 

 factor which allows us to concede to it a fair chance of success. Many seeds 

 furnished with a tolerably large pappus or wing have only about one-fifth 

 the capacity for maintaining themselves in the air which is possessed by 

 the species chosen ; to such as these only a possibility of transport to the 

 island by wind can be conceded. What are we to say of the chances of many 

 of the round-seeded species, whose seeds fall ten to forty times as fast as 

 those of the Epilobium ? 



Transport by Birds. 



The inquiry as to the efficacy of the agency of flying creatures in reference 

 to the flora of Clare Island practically limits itself to the case of birds. Bats 

 are so rare in the district as to be a negligible factor ; and as regards flying 

 insects, while they have often been suggested as possible transporters of 

 small seeds, and in a few cases {e.g. locusts) 1 shown to be so, there is a lack 

 of evidence so far as native insects are concerned. As regards birds, they 

 are unquestionably a potent agent in plant-dispersal. 



Instances of birds being taken carrying in their crops or intestines, or on 

 their feet or plumage, the seeds of various plants, are given by almost all 

 writers on plant-distribution. To quote a few modern instances, Guppy 2 

 took 828 seeds, representing at least ten species, from the stomachs and 

 intestines of thirteen ducks. Ekstarn 3 found the crops of Ptarmigan in 

 Spitzbergen in August filled with vegetable matter, including seeds and 

 bulbils of many species. Holmboe 4 obtained seeds of fifty- three species of 

 plants from the alimentary canal of eighteen species of birds. Or again, 

 from one pound of dried excrement of Corvus americanus taken from the 

 ground under the crow-roost at Arlington, U.S.A., 4764 seeds were obtained, 

 belonging to over half a dozen species. This material represented the deposit 

 lying on four square feet of ground out of about fifteen acres occupied by the 

 roost. The seeds displayed a very high capacity for germination. Many of 



1 Darwin : Origin of Species, 6th ed., p. oil. 



■ H. B. Guppy, Science Gossip, N.S., i, p. 145. 1894. 



3 0. Ekstam : Einige bliitenbiologische Beobachtungen auf Spitzbergen. Tromsb Museums 

 Aarshefter, xx, p. 52. 1S97- 



4 Jens Holmboe : Notizen iiber die endozoische Samenverbreitung der Vogel. Nyt Magazin 

 Naturvidenskaberne, xxxviii, pp. 305-320. 1900. Abstract in Bot. Centralblatt, lxxxviii, p. 81. 



