54 
the leafless species). — Succulent shrubs, very variable in form. Stems usually angular, or 
two-edged, or foliaceous. Leaves almost always wanting ; when present, fleshy, smooth, 
and entire ; or spine-like. Flowers either showy or minute, usually lasting only one day or 
night, always sessile. 
Anomalies. — The calyx and corolla are distinguishable in Rhipsalis, which is also said 
to have its seeds attached to a central placenta. 
Affinities. 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 is rather to be considered a modification of structure which 
may be common to all tribes. Hence the immediate relationship of Cactacese 
is neither with Euphorbiaceae, nor Cassythaceae, nor Asclepiaceae, nor Por- 
tulaceae, nor Asphodelaceae, all of which contain a greater or less number of 
succulent genera. Through Rhipsalis, which is said to have a central placenta, 
Cactaceae are connected with Portulaceae, to wliich also the curved embryo 
of the section of Opuntiaceae probably indicates an approach. De CandoUe 
further traces an affinity between these plants and Mesembryaceae. For an 
elaborate account of this order, see his memoir above quoted. Grossulaceae, 
with which they were foniierly combined, are manifestly different in a large 
number of points. Nuttall separates from these what he calls Spaetalumeae, 
which contain nothing but a certain plant named Lewisia. That species, how- 
ever, seems to be only a Cactus with nearly superior fruit. Nuttall, indeed, 
says that it has not the habit of Cactaceae ; but it is not easy to say what the 
habit is of an order which comprehends such plants as the leafy Pereskias, the 
cord-like Rhipsalis, and the lumpish Melocacti. Lewisia, of which alone 
Spaetalumeae consist, is a sort of leafy MammiUaria. 
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. De Candolle 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 naturalised 
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 
naturalised 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 440 north latitude. There is no reason 
for supposing that the modem Opuntia is described in Theophrastus, as 
Sprengel 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, 
diy, exposed places are the favourite stations of Cactaceae, for which they 
are pecuharly adapted, in consequence of the imperfect evaporating pores 
^^'hich they possess, as compared with other plants ; a circumstance which, as 
De Candolle has satisfactorily shewn, wiU account for the excessively succulent 
state of their tissue. For geographical observations see Martins in Ann. Sc. 
2. ser. 2. 110. 
Properties. The fniit is very similar in its properties to that of Grossula- 
ceae, in some being refreshing and agreeable to the taste, in others mucilaginous 
and insipid ; they are all, however, destitute of the excessive acidity of some 
gooseberries and currants. The fruit of Opuntia vulgaris has the property of 
staining red the urine of those who eat it. The juice of MammiUaria is remark- 
able for being slightly milky, and at the same time sweet and insipid. 
GENERA. 
MammiUaria, Haw. Echinocactus, Salm. Opuntia, Tourn. Rhipsalis, Gsertn. 
Lewisia, Pursh. Cereus, DC. Pereskia, Plum. Hariota, Adans. 
Mclocactus, C. Bauh. Phyllanthus, Neck. 
