INTEODUCTIOlSr. Ixxiii 



type indicated by the first component in tlie compound name, has a 

 tendency to enter the type indicated by the second component. 



Flowering Seasons. — In the case of wide-ranging species the 

 periods given are a mean between the northern and southern 

 flowering seasons for Ireland. In the peculiarly mild and equable 

 Irish climate the flowering period of many species is prolonged far 

 beyond what is usual under the more continental conditions which 

 obtain in Great Britain, and to a greater or less degree the absence 

 throughout southern and south-western Ireland of any well-defined 

 winter season makes it difficult to fix the precise limits of the 

 flowering periods. 



Relations of Soils wnd Plants. — In the following pages special 

 attention has been drawn to the effect exercised by the varied con- 

 stitution of soils on the distribution of plants. While the great 

 mass of the commoner or ubiquitous species exhibit, as a necessary 

 condition of their wide range, an almost absolute indifference in 

 this respect, some smaller groups of plants show in various degrees 

 a preference for, or an aversion from, certain soils. Though very 

 strongly marked in many cases, this preference or aversion perhaps 

 in no instance reaches to absolute exclusiveness. Broadly speaking, 

 the presence or absence of lime in a soil would appear to be the 

 most potent and prevalent cause of the observed preference or 

 aversion, and the terms caleioole and caleifuge most fitly express this 

 relation of plants and soils. A ealcicole species is one which inhabits 

 by preference a soil containing lime in sufficient quantity to give a 

 brisk effervescence with acids ; a calcifage species is one which avoids 

 such a soil ; and the use of these terms does not imply the adoption 

 of any theory as to the precise action of the lime whether direct 

 (chemical) or indirect (mechanical). Following the example of 

 M. Contejean,^ from whom the use of these convenient terms has 

 been borrowed, an attempt has been made in this work to divide the 

 ealcicole and caleifuge species into groups corresponding to the 

 strength of the observed preference or aversion. These groups have 

 been distinguished by the letters A, B, and C. A species marked 

 Caleifuge A is one which very rarely appears on soUs containing an 

 appreciable proportion of lime ; a species marked Caleifuge B, 

 though it may appear not infrequently on lime soUs, is invariably 

 found in far greater abundance and luxuriance on soUs from which 

 lime is absent ; and a species classed as Caleifuge C is one which, 

 though occurring freely in both calcareous a,nd non-calcareous soils, 



graphic Botaniqite — Influence du terrain sur la Vegetation. — Ch. 

 Contejean. Paris, 1881. 



