xUv JNTEODTJCTION. 



mountainB, their deflcienoies in species of tte HigUand type can 

 iaidly be considered anomalous. 



A glance at the following list of the plants of this type foimd 

 in Ireland, numbering 41 in all, will show that they have a marked 

 tendency to a western distribution. Neglecting two species which 

 are confined to the north, it will be seen from the prefixed letters 

 W. and E., that while no less than 36 of the species occur in "West 

 Ireland, only 27 are found in the East. Of the 36 species found in 

 the "West, 12 are absent from the East ; of the 27 found in the East, 

 only 3 are absent from the West. 



Highland Type Plants in Ireland. 



Hieraoium gothicum. 

 H. corymbosum. 

 Arctostaphyloa Uva-ursi. 

 Vaceinium Vitis-Idsea. 

 Polygonum yiviparum. 

 Oxyria digyna. 

 SaKx hertaoea. 

 Juniperus nana. 

 Carex pauciflora. 

 C. rigida. 

 C. aquatiUs. 

 Deschampsia alpina. 

 Sesleria cserulea, 

 Poa alpina. 

 Cryptogramme orispa. 

 Aspidium Lonchitis. 

 Asplenium viride. 

 Lycopodium alpinmn. 

 Selaginella selaginoides. 

 Isoetes laouetris. 



All of the 12 Highland Type plants which in Ireland are confined 

 to the West, occur in West England or Wales, so that it is hard 

 to account for their absence fi-om East Ireland if we assume them to 

 have made part of a great plant migi-ation spreading westward from 

 the European continent across England into Ireland, towards the 

 close of the last Glacial Period. The difference in the character 

 of the eastern and western mountain groups of Ireland certainly 

 seems inadequate to account for these absences. But we are hardly 

 justified in supposing the glaciation of Ii-eland to have com- 

 pletely denuded the country of its plant population. The existence 



