Clare Island Survey — Phanerogamic/,, 10 33 



that have been at work " from the beginning," that it seems wise to keep them 

 in a separate category. 



Man has influenced the flora in many ways, but most of all by clearing 

 away the native vegetation and growing instead certain plants, native or 

 foreign, which are useful to himself. The ousted native species, which have 

 hitherto held the ground against all comers, are continually breaking into 

 these reserves, and man is as constantly employed in keeping them out. 

 Agriculture, indeed, has been defined as " a controversy with weeds." 



The majority of our present-day weeds are light-soil plants widely 

 spread in Europe ; and from the beginning these must have been weeds 

 in the cultivated lands, into which they migrated, and from which they 

 have never since been absent. Similarly, later on, the draining and manuring 

 of the land, the metalling of roads, the planting of trees, all had their effect, 

 both in providing new habitats for indigenous species, and in allowing foreign 

 introduced plants to obtain a footing. 



So one effect of even the earliest cultivation must have been a very con- 

 siderable extension of the range of many native species (as well as the 

 curtailment of the range of others) — just as the erection of mortar-built walls 

 has resulted in the natural migration of calcieole plants, such as the Spleen- 

 worts, into areas which previously furnished them with no suitable habitat. 

 And along with this natural migration into artificial habitats by means of 

 wind- borne seeds, feeding birds, and so on, there went on artificial migration 

 through the medium of seeds imported by man in various ways. From this 

 point of view, then, we have in the farm-land three main classes of plants 

 to deal with : — 



(1) Native species which still maintain their original habitat in the 

 cultivated areas. 



(2) Native species which have migrated by natural means from adjoining 

 aboriginal habitats into the ground altered by man. 



(3) Species carried into the new ground by man, or through his 

 operations. 



As regards the date of the earliest changes in the flora, we know that 

 the cultivation of cereals in Europe goes back to Neolithic times ; and that 

 then, as now, weed-seeds were mixed with the grain. In Ireland, 

 we have no direct evidence of Neolithic agriculture. Among the stone 

 implements, for instance, we do not find sickles, like the flint sickles of 

 ancient Egypt — unless a certain curved knife of slate from Antrim, 1 sharpened 

 on the concave face, may be looked upon as such. But the grain-rubbers 



Sir John Evans : The Ancient Stone Implements of Great Britain, p. 35S. 1897. 

 B. I. A. PKOO., VOL. XXXI. E 10 



