THE COUNTY KECOEDS xcv 



clature of " Cybele Hibernica." As explained in the same place, 

 hybrids and varieties are omitted. An exception, however, is made 

 in the varieties of certain critical plants, such as Raminculi, liubi, 

 Rosce, Hieracia, on account of the instability of the grouping of these 

 forms. Alien plants naturalized in only one locality are usually 

 omitted, such as Valerianella carinata, Artemisia Stelleriana, Senecio 

 viscosus, Cineraria maritima, Mentha Requienii, Polygonum sagitti- 

 folium, SisyrincJiiicm calif ornicum, since their present claim to 

 admission to the flora may depend on local and temporary in- 

 fluences. A few plants now generally considered hybrids, such as 

 Rosa liihernica, Rosa involnta, Potamogeton Zizii, and Carex axillaris, 

 are admitted because their hybrid origin is not yet proved beyond 

 doubt, and their familiar names would be missed in a list of Irish 

 plants. 



Clarendon type is used for species, italic type for plants which 

 are considered as sub-species, and not reckoned separately in the 

 statistics, &c., as already explained. 



The signs *, |, f, are used in their ordinary significance of 

 certainly, probably, or possibly introduced. Where prefixed to the 

 name of a species, they refer to its general standing in Ireland, and 

 where similar marks are not prefixed to the division-records, they 

 may beheld to govern all of these. 



Census numbers. — The census line, succeeding that which con- 

 tains the name of a plant, shows (1) the total number of divisions 

 in which it occurs, and (2) its distribution according to a tripartite 

 division of Ireland into East, Centre, and West. This tripartite 

 division is shown on Map III. The Eastern group consists of 15 divi- 

 sions, the Centre of 13, the West of 12 ; the three are of approxi- 

 mately equal area, namely : — Eastern division 10,996 square miles, 

 Centre 10,237 square miles, Western division 11,290 square miles. 

 The dividing lines in north and south between the Eastern and 

 Western groups represent the natural meeting-ground of the char- 

 acteristic east coast and west coast floras, though, of course, the two 

 overlap to a certain extent. The numbers in the list of divisions 

 which succeeds the census-line give at a glance a rough idea of the 

 north and south distribution of a plant, accordingly as they are 

 mostly tens or twenties or thirties ; Map III. shows the significance of 



