556 NATIVE AND NATURALIZED BRITISH SPECIES. [June, 



bution, they will notwithstanding have a tendency to enlarge the 

 circumference of their locale, to extend their horizontal and ver- 

 tical range, and to embrace a larger space. 



This tendency will increase with the increase or diminution of 

 temperature, or with atmospheric changes attendant on cultiva- 

 tion ; or it may, in certain cases, depend on the neglect of culti- 

 vation. In densely-peopled Europe, however, it is but seldom 

 that the neglect of culture extends the range of plants ; cultiva- 

 tion frequently does. We know that during the last three cen- 

 turies this cause, the extension of tillage, has been very efficient 

 in promoting the dispersion of plants. Our flora has increased, 

 and is still increasing rapidly ; this fact has often been held up 

 to the notice of our readers. 



The nativity of a plant is not to be ignored or denied simply 

 on the ground that it is not found everywhere from the Lizard 

 Point to Wick or John-o'- Groat's House. Botanists who only 

 see a straggler, like Senebiera didyma, here and there about 

 London and York, say it is not a native. Probably it is not, in 

 their very restricted sense of the term. Yet those who see it 

 about King's Wood, and other places near Bristol, have no hesi- 

 tation in admitting its claims. 



The Wallflower probably is not so common on walls in Scot- 

 land as it is in the neighbourhood of London and on the ancient 

 castle of Guildford, but this is no suflBcient reason for denying 

 its nativity. Again, as this plant (Wallflower) is not known to 

 grow anywhere Ijut on such places as rocks and walls, where it 

 grows here, and consequently there is the same objection to its 

 admission as a native of anywhere, the onus probandi lies upon 

 those who deny the nativity the plant, not on those who assert 

 it.* It may be a native of several places, as of France and Ger- 

 many, but why not that of England ? The reason given for this 

 denial is equally valid for denying its nativity in all other places, 

 viz. its growing on walls, oa artificial erections. If this principle 

 were strictly carried out, at least one- half of the plants usually 

 deemed British would be expunged from our national catalogues, 

 and for what object? The maintenance of the purity of our 

 flora. 



* Our correspondent appears to have forgotten that the Wallflower grows plenti- 

 fully on the sea-margin in that bleak part of the coast of England between the 

 South Foreland and Dover Castle. — Ed. 



