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 description 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 of the 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." 



