Praeger — On Tijpes of Distribution in the Irish Flora. 23 



to be clue largely to suitability of soil, partly to conditions of 

 climate. 



(2) Scottish and Highland. These are the northern plants, the 

 latter an intensified group of the former. In Ireland they are concen- 

 trated in the north, spreading somewhat abundantly down the western 

 coast, much more sparsely along the eastern. It should be noted that 

 the distribution in England and Wales of these plants offers many 

 points of resemblance to their Irish range, though the species extend 

 somewhat further southward in the larger island. As in Ireland, the 

 group spreads far down the west coast of England, much less so down 

 the eastern, so that, on a rough examination, South "Wales appears to 

 contain as many " Scottish " plants as the Trent province. Physical 

 conditions will suggest themselves in explanation of this in a manner 

 not applicable to Ireland, where the problem is more difficult of solu- 

 tion. A line drawn north-eastward from the Bristol channel to the 

 Wash will cut off, on the northward, most of these plants ; and this line 

 would appear to correspond well with one in Ireland di'awn from the 

 Shannon mouth to Dundalk Bay. 



To account for the greater abundance of alpine plants in the west 

 than in the east of Ireland, the suggestion has been made, in *'Cybele 

 Hibernica," ed. ii., and elsewhere, that during the Glacial Period the 

 mantle of ice drove these species downward to the seaboard in the milder 

 west, whence, on the retreat of the ice- sheet, they colonized the western 

 mountains. This appears as likely a hypothesis as can be put forward. 

 But the similarity of the range of "Highland" and of "Scottish" 

 species suggests that at least some of the " Highland " plants, which 

 in Ireland are not alpine in range, may have come into Ireland with 

 the " Scottish" plants, many of which probably colonized this country 

 from the north-east. Another point to be remembered is that — pre- 

 sumably on account of greater moisture — the west of Ireland is un- 

 doubtedly more suited, even at low elevations, to the growth of alpine 

 plants than the eastern, and the " lo-vs^est limit " line, which for many 

 species almost touches sea-level along the west coast, may, in the east, 

 pass above the tops of the mountains. 



(3) Atlantic. In England south-western, and including a consider- 

 able number of maritime plants. This is the hygrophile element of 

 the English flora, composed of plants which prefer the equable tempe- 

 rature and abundant moisture that pertain to an insular climate. In 

 Ireland the group is rather southern, distributed in fair proportion 

 round the southern half of the littoral, but many of the species occur 

 round the greater part of the Irish coast. 



