64 



Affinities. It has been already remarked, on more than one occasion, in 

 this work, that the state of anamorphosis, or, in other words, that remarkable 

 distension or increase of the cellular tissue of vegetables, from which the name 

 of succulent is derived, is no indication of natural affinity, but rather to be con- 

 sidered a modification of structure which may be common to all tribes Hence 

 the immediate relationship of Cactese is neither with Euphorbiaceas, nor Lau- 

 rineae, nor Asclepiadeae, nor Ficoideae, nor Portulacese, nor Asphodeleee, all of 

 which contain a greater or less number of succulent genera ; but with Gros- 

 sulaceffi, in which no tendency whatever to anamorphosis exists. The dis- 

 tinction between the two orders is mentioned under Grossulaceae. Through 

 Rhipsalis, which is said to have a central placenta> Cactese are connected with 

 Portulaceaa, to which also the curved embryo of the section of Opuntiaceae 

 probably indicates an approach. Decandolle further traces an affinity between 

 these plants and Ficoidese. For an elaborate account of this order, see his 

 memoir above quoted. 



Geography. America is the station of the order; no species appearing to 

 be natives of any other part of the world ; in that country they are abundant 

 in the tropics, extending a short distance beyond them, both to the north and 

 the south. Decandolle states that 32° or 33° north latitude is the northern 

 limit of the order ; but it is certain that a species is either wild or naturalized 

 in Long Island, in latitude 42° north, and that there is another somewhere 

 about 49°, in the Rocky mountains. The species which are said to be wild 

 or naturalized in Europe, Mauritius, and Arabia, have been introduced from 

 America, and having found themselves in situations suitable to their habits, 

 have taken possession of the soil like actual natives : in Europe this does not 

 extend beyond the town of Final, in 44° north latitude. There is no reason 

 for supposing that the modern Opuntia is described in Theophrastus, as Spren- 

 gel asserts ; the description of the former writer applying, as far as it applies 

 to any thing now known, rather to some tree like Ficus religiosa. Hot, dry, 

 exposed places are the favourite stations of Cacteee, for which they are pecu- 

 liarly adapted, in consequence of the small quantity of evaporating pores 

 which they possess, as compared with other plants ; a circumstance which, as 

 Decandolle has satisfactorily shown, will account for the excessively succu- 

 lent state of their tissue. 



Properties. The fruit is very similar in its properties to that of Grossu- 

 laceee, some being refreshing and agreeable to the taste, others mucilaginous 

 and insipid ; they are all, however, destitute of the excessive acidit}^ of some 

 gooseberries and currants. The fruit of Cactus opuntia has the property of 

 staining red the urine of those who eat it. The juice of Cactus mammillaris 

 is remarkable for being slightly milky, and at the same time sweet and insipid. 



Decandolle has the two following sections, the characters of the last of 

 which are not, however, very certainly ascertained to be correct : 



1. Opuntiace^. 



Ovula and seeds parietal. 



Examples. Cactus, Opuntia, Mammillaria. 

 II. Rhipsalide^:. 



Ovula and seeds attached to a central axis. 



Example. Rhipsalis. 



