326 POPULAR GEOGRAPHY OF PLANTS. 



clothe our island were blooming and filling the air with 

 their odour. 



By a recent theory which has been put forward by the 

 late lamented Professor Edward Forbes, he supposes that 

 England is proved, by the identity of the species both of its 

 animals and its plants (its fauna and flora) with those of 

 adjacent countries, to have been at some previous time 

 united to them. As flowers are the subject with which we 

 are concerned, we will confine our attention to them. As 

 a necessary basis of this theory, it is first assumed that all 

 the individuals of each distinct species have descended from 

 a single flower, or, in the case of monoecious and dioecious 

 plants, from a single pair; and it is stated that the very 

 idea of a species implies that the individuals which compose 

 it are thus related to one another. This is called the ex- 

 istence of a specific centre. 



To show, by contrast, the probability that plants of the 

 same identical species have been thus disseminated from one 

 original centre, Professor Forbes points to the fact that 

 species which are found in situations so remote (for instance 

 in opposite hemispheres) as to forbid all idea of any pre-exist- 

 ing connection, are not found to be exactly alike, they 

 are not identical, that is to say, but only representative. 



He then points to another fact, namely, that the same 



