10 54 Proceedings of the Royal Irish Academy. 



* Lapsana communis. N Eumex obfcusifolius. 

 N Sonchus oleraceus. „ iFestuca ovina or 



* Atriplex patula. ^F. rubra. 



* Polygonum Persicaria. Grass, sp. 



* P. lapathifolium. 



It will be seen that all the seeds which could be identified belong to , 

 species which already occur on the island, four of them as common natives ; 

 the rest, six in number, as weeds, mostly abundant. 



Mud from the Mainland. — To see whether plants were being introduced 

 from the mainland by means of mud adhering to the feet of men or animals, 

 I had the boots of an island man (Pat Grady) scraped on his arrival on the 

 island in November from Carrowraore, after a couple of days spent in 

 Louisburgh. The material was sieved, and on being kindly examined by 

 Miss Knowles, yielded seeds as follows : — 



Stellaria media, Polygonum ?aviculare, 



Conium maculatum, Juncus ?bufonius, 



Sonchus asper, Juncus sp., 



?Anagallis arvensis, Holcus lanatus, 



and about six more species, indeterminable. 

 It will be noted that these are all plants common about houses and road- 

 sides, and the list is suggestive as indicating the ease with which roadside 

 plants attain ectozoic dispersal. 



6. OEIGIN OF THE FLOEA. 



In attempting to arrive at a conclusion as to the manner in which the 

 present flora reached and became established on Clare Island — whether by 

 means of a former land-connexion, or across the existing three-mile strait that 

 separates the island from A chill on the north or the Eoonah district on the 

 south-east — we may, without having recourse to geological evidence, learn 

 much from a study of the plants themselves. For this purpose we turn our 

 attention to the means by which the species composing the flora increase, and 

 spread, and migrate, and especially to the question of seed'-dispersal. In 

 the case of the majority of the lower plants — Algae, Lichens, Fungi, Mosses, 

 Liverworts, Horsetails, and Ferns — their spores are extremely minute and 

 light, and are known to be capable of almost limitless dispersal by air 

 currents ; indeed, these spores may almost be reckoned as one of the normal 

 constituents of atmospheric dust in temperate and tropical regions. The 



1 I follow the example of Bentham and others in applying the term seed to what, as Clement Reid 

 says, is its "popular and original use" — i.e. that which is sown; in other words, the unit of 

 dispersal. Nothing is to be gained from the pedantic repetition of the phrase "seeds or fruits" 

 over and over again in the pages which follow. 



