I902. Reviews. 19 t 



to be some confusion of thought implied, too, in the reference to succes- 

 sive waves of plant migration, since the question under discussion is 

 merely the floral re-peopling of Ireland on the close of the last glacial 

 period. 



The second, and for Irish botanists the more interesting, section of 

 the paper deals with what may be called the internal relations of the 

 Irish flora. About two-thirds of our Irish species have been arranged 

 by Mr. Praeger under seven types. One of these, the General type, calls 

 for no remark. Of the remaining six, all of which demand careful dis- 

 cussion, four are well recognised, while two others, the Central and the 

 Marginal, are here proposed for the first time. 



First in order comes the Central type, defined as made up of species 

 found chiefly in the Central Plain, and often extending to the margin of 

 the island on the east and west, but showing a marked restriction of 

 range towards the north and south. The north and south range laid 

 down for this type appears to be little less liberal than its east and west 

 range, the northern boundary being a line joining Sligo Bay and 

 Dundalk Bay, the southern a line joining Waterford with the Shannon 

 mouth (pp. 32-33). The title, Central, here is somewhat ambiguous. 

 Though suggesting a purely inland area, it is applied to one which 

 stretches right across Ireland from sea to sea. If the term is to be used 

 in the former sense, and the placing of the focus of the group in West- 

 meath would seem to show that this is the author's intention, no less 

 than ten species, which range right across the island without showing 

 any marked increase towards the centre, should be excluded. These 

 species are — Poterium Sanguisorba^ Myriophyllum verticillattim^ Erigeron acte^ 

 Carlina vulgaris, Centaurea Scabiosa, Crepis taraxacifolia^ Tragopogou pratense^ 

 Gentiana Amarella^ Jtincus obtusijloriis, and Lemna polyrhiza. Along with 

 these might be placed a few others, such as Thalictriwi Jlavtim, Cornus 

 sanguinea, Ophrys niiiscifera, and Eqiiisetuvi variegatum, whose focus is very 

 doubtfully Central, the number of the Central type species being thus 

 reduced from 36 to 22. The chart on p. 36 shows the inappropriate 

 focussing of the group whose development in the western division of 

 S.B. Galway is little less full than it is in Westmeath. Median might be 

 suggested as a better title for the group than Central, and were this 

 title to be adopted, the objections just made would lose much of their 

 weight. But the institution of a Median type would appear to demand 

 a tri-partite division of the island into Northern, Median, and Southern, 

 and whatever the advantages of such a scheme might be, simplification 

 would not be one of them, since the very natural groups of eastern and 

 western plants could not be merged in any of the three divisions. 



While the distinctive feature of the Central type is aggregation, the 

 criterion of the Marginal type is, in a certain sense, dispersion. This 

 type is defined as made up of plants, " 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 Central 

 Plain" (p. 33). We should expect to find plants of this type occurring in 

 a large proportion of such of the topographical divisions of Ireland as are 



