156 



REAUMURIACE.E. II. HOLOLACHNA. CACTE^E. 



Cult. Elegant little shrubs of easy culture ; they thrive best 

 in a mixture of sandy loam and peat ; and young cuttings readily 

 strike root under a hand-glass. 



II. HOLOLA'CHNA. This genus having already been de- 

 scribed under the order Tamaracinees, it is only necessary here 

 to refer to vol. II. p. 728. where all the details of the genus will 

 be found. 



ORDER CXVII. CA'CTEjE (this order contains the genus 

 Cactus, and all the genera recently separated from it). D.C. 

 prod. 3. p. 457. mem. cact. in mem. mus. vol. 17. p. 1-119. 

 Cactoideae, Vent. tabl. 3. p. 289. Nopaleae, D. C. theor. 

 elem. 216. Cacti, Juss. gen. p. 310. exclusive of Grossu- 

 larieae. Opuntiaceee, Juss. diet. 35. p. 144. exclusive of Gros- 

 sularieae. H. B. et Kunth, nov. gen. amer. 6. p. 65. Cactus, 

 Lin. gen. no. 613. Willd. enum. hort. berol. p. 30. Link, 

 enum. 2. p. 21. &c. 



Calyx composed of many sepals, usually indefinite in number, 

 and confounded with the petals, united and adnate a great 

 length to the ovarium ; with the tube smooth in the genera Mam- 

 millaria, Melocdctus, and Rhipsalis ; or with the lobes of the se- 

 pals crowning the fruit, and having the tube scaly as in the genera 

 Ccreus, Opuntia, and Pereskia. Petals disposed in two or more 

 series, hardly distinguishable from the inner sepals, and some- 

 what united to them ; sometimes irregular, and disposed in a long 

 tube at the base, but distinct at the apex, as in the genera Mam- 

 millaria, Melocdctus, and Cereus ; sometimes equal and distinct 

 to the very base, forming a rotate corolla, as in the genera Opun- 

 tia, Pereskia, and Rhipsalis. Stamens indefinite, disposed in 

 many series, more or less cohering with the petals or inner 

 sepals ; filaments slender, filiform : in the genus Opuntia they 

 are irritable to the touch ; anthers ovate, versatile, 2-celled. 

 Ovarium obovate, fleshy, 1-celled: with numerous ovula, ar- 

 ranged upon parietal placentas, which are equal in number to the 

 lobes of the stigma. Style filiform, sometimes full and sometimes 

 fistular ; stigmas numerous, cither spreading or collected into a 

 cluster. Fruit fleshy, 1-celled, many-seeded, either smooth and 

 crowned by the calyx, or covered with scales, scars, or tuber- 

 cles, and umbilicate at the apex. Seeds, when young parietal, 

 but when mature imbedded in the pulp with which the cells are 

 filled, oval or obovate, without albumen. Embryo either straight, 

 curved, or spiral ; with a short, thick, obtuse radicle ; cotyledons 

 flat, thick, foliaceous in Opuntia and other leaf-bearing genera, 

 very small in Melocdctus, and perhaps almost obsolete in Mam- 

 millaria and other leafless genera. 



This order contains fleshy or succulent shrubs, very variable 

 in habit. Stems usually angular, winged, or regularly beset with 

 tubercles, rarely terete, usually jointed ; joints compressed. 

 Leaves usually wanting, but when present small, caducous, and 

 terete, sometimes like those of Sedum, rarely flat and expanded, 

 sometimes alternate and disposed in a spiral order, always gla- 

 brous and fleshy. Prickles or bristles disposed in fascicles, 

 rising from the axils of the leaves ; in the leafless genera the 

 fascicles of spines are disposed on the angles of the stem, rising 



from tubercles. Flowers very variable, showy, or minute, usually 

 solitary, sessile, rarely in fascicles, ephemeral, expanding by 

 night or by day. 



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

 this work, that the state of that remarkable distention or in- 

 crease of cellular tissue of vegetables, from which the name of 

 succulent is derived, is no indication of natural affinity, but rather 

 to be considered a modification of structure, which may be com- 

 mon to all tribes. Hence the immediate relationship of Cdctece 

 is neither with Eupfiorbiacece, nor Laurmece, nor any other tribe 

 of succulent plants, but with Grossularieix, in which no tendency 

 whatever to an increase of cellular tissue exists. Through Rhip- 

 salis, which is said to have a central placenta, Cacleae are con- 

 nected with Purtulacece, to which also the curved embryo of the 

 section of Opuntiacece probably indicates an approach. De Can- 

 dolle further traces an affinity between these plants and Ficoidece. 

 For an elaborate account of this order, see his Memoir above 

 quoted. 



The fruit is very similar in properties to those of Grossularia, 

 some being refreshing and agreeable to the taste, others mucila- 

 ginous and insipid ; they are all, however, destitute of the ex- 

 cessive acidity 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 Mammillaria vulgaris is remark- 

 able for being slightly milky, and at the same time sweet and 

 insipid. 



Synopsis of the genera. 

 TRIBE I. 



OPUNTIA % CE. Ovula, and therefore the seeds, fixed to the 

 parietes of the fruit. 



1 MAMMJLLA'RIA. Tube of calyx adhering to the ovarium ; 

 lobes 5-6, coloured, crowning the young fruit. Petals 5-6, 

 hardly distinguishable from the calyx. Stamens disposed in many 

 series. Stigma 5-7-cleft. Berry smooth. 



2 MELOCA'CTUS. Tube of calyx adhering to the ovarium ; 

 lobes 5-6, petaloid, crowning the young fruit. Petals 5-6, united 

 into a long tube with the sepals. Stamens disposed in many 

 series. Stigma 5-rayed. Fruit smooth. 



3 ECHINOCA'CTUS. Sepals numerous, imbricate, adhering to 

 the ovarium : outer ones in the form of an involucrum : inner 

 ones petal-formed. Stamens numerous. Style multifid at the 

 apex. Berry scaly from the remains of the sepals. 



4 CE'REUS. Sepals very numerous, imbricate, adnate to the 

 base of the ovarium, united into an elongated tube : outer ones 

 shorter and like a calyx : middle ones longer and coloured, 

 innermost ones petal-formed. Style multifid at the apex. Berry 

 areolate, tubercular or scaly from the remains of the sepals. 



5 EPIPHY'LLUM. Tube of calyx very long, furnished with 

 remote scales ; limb of corolla multifid, rosaceous or ringent. 

 Branches flat. 



6 OPU'NTIA. Sepals numerous, leaf-formed, adnate to the 

 ovarium : upper ones flat and short : inner ones petal-formed, 

 obovate and expanded, with no tube above the ovarium. Sta- 

 mens numerous, shorter than the petals. Stigmas numerous, 



