VALIDITY OF SPECIES 441 



Aponogeton, a Cape plant, not native of cold regions, beara 

 a freezing every winter in our ponds : no one would have 

 dreamt of it. 



Edinburgh : July 1845. 



I am exceedingly glad that TEspece [by Godron] has 

 interested you, and will try and get you a copy from Mon- 

 tagne, through whom my father received this. I am not 

 inclined to take much for granted from any one who treats 

 the subject in his way and who does not know what it is to 

 be a specific Naturalist himself. Those who have had most 

 species pass under their hands, as Bentham, Brown, Linnaeus, 

 Decaisne, and Miquel, all I believe argue for the vaHdity of 

 species in nature ; they all direct attention to the cases where 

 salient characters are unimportant, though taken advantage 

 of by the narrow-minded studiers of overwrought local floras, 

 and these facts, thus noticed as cautions to others, are taken 

 up by such men as Gerard, who have no idea what thousands 

 of good species there are in the world. Nature may have 

 both made and muddled species ; we shall never know what 

 are species in some genera and what are not. Generally 

 cultivation will prove the validity of a species ; Gerard says 

 that ' varieties of apples, &c. are more distinct than many 

 species,' but how soon all revert to crabs ; again, the wheat 

 is always adduced as a permanent variety of some unknown 

 plant and it ought on that account to rank as a species, but I 

 do not think so because it will never run wild ; it is to me 

 very marvellous that the wheat seed is destroyed by being 

 left in the ground of our country and that we see so little 

 next year on a field that has supported milHons of ears during 

 the present. 



Gerard evidently is no Botanist, he talks of having 

 found both Prunus s^pinosa and Ruhus rusticans without 

 spines. Now spines are only abortive branches, and their 

 absence or presence is never, of itself, a botanical character ; 

 as a spine is not an organ per se : and again, no Bubus ever 

 had or ever wiM have spines ; the 'prickles of Bubus are mere 

 appendages of the cuticle and have no organic connection 

 like spines with tlie pith and wood of the plant : species vary 

 in the prickliness, just as they do in hairiness, according to 

 the amount of spines or hair produced ; but they vary in 

 spininess according to the number of branches that are 



