340 PLANT-BREEDING 



times of cold and of subsequent repeated migration, how 

 can we know under what circumstances they originated? 

 Observation teaches which of the life-conditions available at 

 the present time are the best suited for them, but there is 

 no reason to assume that they have been produced under 

 similar ones. Plants originally inland forms may now 

 prefer the sea-shore, because they are crowded out else- 

 where, and many an alpine plant would without doubt 

 prefer a lower and warmer region were it not for dread of 

 the enemies it has to meet there. 



Opposed to the common plants, which have evidently 

 migrated far from their place of birth, are the so-called 

 local species, which inhabit only one mountain, or one valley, 

 or are limited even to the slope of a single hill. Here, 

 at first sight, two possibilities occur. The species may be 

 of recent origin, and may not as yet have found time for 

 spreading itself outside of its native spot. Or it may be 

 old, perhaps slowly dying out. In this case it may once have 

 been distributed over large areas, but have disappeared 

 from almost all points. Only there where it enjoyed 

 sufficient isolation or sufficiently suitable life-conditions 

 has it survived. The study of these conditions may then 

 show us the minimum of requirements for continuing its 

 existence, but it does not tell in any way how these precious 

 qualities may have originated. Who does not remember the 

 description of the bright dark-blue Wulfenia, as given by 

 Ouida in her "Moths" (II 271), when Correze brought 

 this rare plant from the- almost inaccessible heights of the 

 Gartnerkugel in Carinthia? There it grew upon the slopes 

 of the mountain, and nowhere else in all the world was it 

 found. Evidently it is only a relic of times that have passed 

 away. 



How can we determine whether in any given case a 

 local species is nearer its origin than its decline? In most 



