species is perhaps more complicated than that of any other 
section. It appears pretty well made out that M. Lamarck 
and myself have united as varieties under the name of Cactus 
opuntia, some species which are truly distinct ; but I also think 
that since that time Botanists have gone too far in describ- 
ing as species a heap of varieties probably originated in 
cultivation, and the flowers of which are still unknown. 
The descriptions of Opuntias made from wild plants corre- 
spond so ill with those made in gardens, that it is almost im- 
possible to identify them, considering the negligent manner 
in which travellers have described them. Thierry de Me- 
nonville, who to be sure was an indifferent botanist, but who 
gave his entire attention to the study of Nopals, says ex- 
pressly, “that if Linnaeus justly complained that the species 
of Cacti with angular stems were inexactly described, we 
may be sure that the deseription of Opuntias is still more 
incomplete, both with regard to number and form. There 
exist in Mexico thirty species, very different from all that 
have been described; and I have had neither the time nor 
the liberty to describe them.” 
“ The principal characters hitherto employed are the 
form of the joints and the spines. The first of these charac- 
ters is to be depended upon only when the mean of all the 
Joints of an individual is taken into account, for there are 
few Nopals of any size, the same individual of which will not 
furnish joints of different forms. As to the spines, their 
number is often variable on the same individual, and all 
travellers say the same species may have them or be 
without them ; their length is not more constant, and varies 
within such extensive limits, according to the mode of cul- 
ture, that we can scarcely give it any importance. The 
garden Nopals, in general, have them less numerous and 
smaller than the wild plants. The colour ofthe spines seems 
somewhat less variable, but as yet we have upon this subject 
nothing but garden observations, made upon individuals pro- 
pagated by cuttings of each other, and we do not know 
whether these characters come thus from seeds. I therefore 
consider the principal part of the Nopals with yellow flowers 
as of doubtful species.” 
