Praeger — On Typea of Distribution in the Irish Flora. 59 



genous materials any group of Ii-ish plants " ctiefly seen about the 

 mountains." The peculiar range of the Irish high-level plants — often 

 absent from lofty mountains in the east and present on hills of less 

 elevation or on low grounds in the "^est — is best brought out by treat- 

 ing them with the other plants of similar distribution. 



So much for the facts. The causes which lead or have led to the 

 distribution of the flora as we now find it are difficult to determine. 

 The efiect produced by the distribution of lime, and of open light 

 soils, is fairly clear ; but climatic effects are not so easily dealt with. 

 As regards temperature, some of the characteristic plants of Connacian 

 type are without doubt frigofuge — in other words, their chief need in 

 OTU' climate is a sufficiently high winter temperature ; and in fig. 60, 

 which shows the isotherms of the coldest month of the year in Ireland 

 (January), parallelis between isophytic and isothermal lines may easily 



Fig. 6o. — January isotherms. 



FiG. 6i. — Julj- isotherms. 



be drawn from among the plants of the south and west. Fig. 61 like- 

 wise, showing the isotherms of the warmest month (July), suggests 

 that a number of the south-eastern species may be thermophiles — 

 plants for which the most pressing need is a high summer temperature 

 for the ripening of fruit. Questions of rainfall probably effect but little 



