VALIDITY OF SPECIES 441 
Aponogeton, a Cape plant, not native of cold regions, bears 
a freezing every Avinter in ovir ponds : no one would have 
dreamt of it. 
Edinburgh : July 1845. 
I am exceedingly glad that I'Espece [by Godron] has 
interested you, and will try and get you a copy from Mon- 
tague, 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, 
DecaisnOj and Miquel, all I beheve 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 millions of ears during 
the present. 
Gerard evidently is no Botanist, he talks of having 
found both Prunus spinosa 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 Rubus ever 
had or ever will have spines ; the prickles of Ruhus are mere 
appendages of the cuticle and have no organic connection 
like spines with the pith and wood of the plant : species vary 
in the prickliiiess, 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 
