Praeger — On Ti/pes of Distribution in the Irish Flora. 33 



chiefly in the Central Plain. While plants of this type often extend 

 to the margin of the island in the east and "west, they show a marked 

 restriction of range towards the north and south. 



The area of the Central type of distribution maybe defined as being 

 limited by a line joining the Shannon moiith with Waterford on the 

 south, and a line joining Sligo Bay with Dundalk Bay on the north, 

 while in its most characteristic form it does not touch either the 

 eastern or western margin of the island. The circle on fig. 21 approxi- 

 mately defines its ideal boundary. 



The Marginal type, which is generally speaking the converse of 

 this, hardly requires defijiition, as its name is sufficiently descriptive. 

 The plants which belong to it are characterized by a tolerably even 

 though frequently discontinuous range through those divisions which 

 lie around the margin of the island, and by an avoiding of the Limestone 

 Plain. The negative character of avoidance of the Central Plain is the 

 most striking feature of this type of distribution ; and the ring which, 

 marks the range of the constituent species frequently thickens consider- 

 ably in the north and south, where the coast-line lies far from the 

 edge of the plain. The area of the Marginal type of distribution may 

 be described as lying outside the circle on fig. 21. 



A number of the rarer and more interesting plants of Ireland are 

 more or less marginal in distribution (being rare in the Central Plain), 

 but are restricted to limited areas ; while many others show a general 

 increase towards the north, south, east, or west of the island. As 

 regards these, the strongest phytological boundary which developed 

 itself is one which corresponds with the curves evolved fi'om a consider- 

 ation of the range in Ireland of the northern and southern plants of 

 Great Britain (see fig. 12) ; and this boundary can be best localized by 

 drawing a Hne from Galway Bay on the west to Dundalk Bay on the 

 east. The need of a dividing line between eastern and western plants 

 also became clear ; and the most natural boundary appeared to be a 

 line passing through the cities of Londonderry and Cork — a division 

 which corresponds with, the partition into eastern and western akeady 

 employed in " Irish Topographical Botany." 



The central circle and these two intersecting lines, then, define six 

 types of distribution which. I believe are founded on the actual range 

 of plants in the country. The names most conveniently employed for 

 the "types" will be 



2. Central. 5. Mumonian. 



3. Marginal. 6. Lagenian. 



4. TJltonian. 7. Connacian. 



R.I.A. PROC, VOL. Yin., SEC. B.] i) 



