DATISCACEA. 501 
1. Datisca glomerata, Benth. et Hook. loc. cit. p. 845. 
Tricerastes glomerata, Presl, Reliq. Heenk. ii. p. 88, t. 64. 
Catirornia.— Mexico, Western Mexico (Henke). 
Order LXV. CACTACE. 
Cactee, Benth. et Hook. Gen. Plant. 1. p. 845. 
With the exception of one or two species of Rhipsalis, which extend to Africa, 
Mauritius, and Ceylon, this family is exclusively American, though some species of 
_Nopalea and Opuntia are now so thoroughly naturalized in certain parts of the Old 
World, especially in the Mediterranean region, as to have all the appearance of being 
indigenous. Indeed some botanists incline to the opinion that some of the species 
may be really indigenous there, just as other families and genera are represented in 
the two continents by closely allied, though undoubtedly endemic, species. Bentham 
and Hooker reduce the number of genera to thirteen. The forms are very numerous; 
but it is very difficult to make an estimate of the number of species. The greater 
part of the following names were applied to forms cultivated in European gardens and 
described by horticulturists in horticultural periodicals ; and a large number of them 
could not possibly be employed in a scientific revision of the family. Many of the 
so-called species were founded upon single plants received in a dead state; and the 
descriptions are very incomplete. Again, a considerable proportion are simply 
characterized by external differences, their flowers never having been seen by the 
describers. Doubtless, too, the selfsame forms have often received more than one 
name. In some cases no descriptions have been found. However, after making all 
due allowances, the species are very numerous; and they find their greatest concen- 
tration in Mexico, rapidly decreasing in numbers northward, the extreme limit reached 
being about 50° N. lat. In the West Indies the number of species is comparatively 
small; but they abound in some parts of Tropical and Subtropical South America, and 
a few occur in the temperate regions of Chili. The estimated number of species 
under each genus is in all cases taken from Bentham and Hooker (‘Genera Plan- 
tarum’); and sometimes their number does not by any means agree with the number of 
names enumerated here. The majority of the names are taken up in Walpers’s 
‘Repertorium,’ vols. ii. and v., and the ‘Annales,’ vol. ii. 
Tribe ECHINOCACTEA. 
1. MELOCACTUS. 
Melocactus, Link et Otto in Verhandl. Preuss. Gartenb. Verein, i. p. 417; Benth. et Hook. Gen. 
Plant. i. p. 847. _ ; 
About thirty species, inhabiting Mexico, Brazil, West Indies, and Colombia. 
