709 



CACTACE^I. 



CACTUS. 



710 



species : in these instances however it is worthy of remark that as 

 the stems advance in age the angles fill up, or the articulations dis- 

 appear in consequence of the slow growth of the woody axis and the 

 gradual development of the cellular substance ; so that " at the end 

 of a number of years, which vary according to the species, all the 

 branches of Cactacece, however angular or compressed they originally 

 may have been, become trunks that are either perfectly cylindrical 

 or which have scarcely any visible angles. This metamorphosis is 

 one of the causes which render it so difficult to identify species that 

 have been described in their native localities from full-grown speci- 

 mens with such as are cultivated in the gardens of Europe." The 

 greater part of the species have stems which are more or less 

 elongated, but in some they are spherical, as in the whole genera 

 Melocactus and Echiiiocctctus. Whatever may be the form of the stem, 

 they usually bear upon their surface little tubercles which at an early 

 age lose the leaves. Those organs however rapidly fall away, and are 

 succeeded by tufts of hairs or spines hooked backward at the ends, 

 and then the species have the appearance of being perfectly leafless. 



Ifclocactus comtnunis. 



All the species are believed to be natives of America, whence how- 

 ever some of the Opuntias have been so long introduced to the Old 

 World that they have here and there taken possession of the soil, and 

 appear like aboriginal inhabitants. Such is the case on the volcanic 

 Boil of ,<Etna, and in various places on the shores of the Mediterranean ; 

 and this has led to the erroneous idea entertained by Sprengel and 

 others, that the Opuntia of Theophrastus was the Opuntia rttlgarit of 

 modern botanists. The Cactacete are chiefly found in the tropical 

 parts of America, a few species only escaping from those countries ; 

 as, for example, to the southern states of North America and to the 

 highlands of Chili and Mendoza. They principally occur on hot dry 

 rocks or plains where the commoner forms of vegetation could not 

 exist, and may be considered one of the means which nature has 

 provided for the support of man in regions where neither food nor 

 water can be procured. Their steins are filled with an abundant 

 insipid wholesome fluid, and their fruit is succulent and in many cases 

 superior to that of European gooseberries. In the fevers of their 

 native countries they are freely administered as a cooling drink, and 

 being bruised they are esteemed a valuable means of curing ulcers. 

 For the sake of such their uses, because of their rapid growth, and 

 especially on account of the numerous spines with which they are 

 armed, the Opuntias or Tunas, aa the Spanish Americans call them, are 

 much planted round houses as fences, which neither man nor animals 

 can easily break through. They are not unfrequent in the dry forest- 

 lands of Brazil, but are said never to occur in the damper parts of the 

 country. In stature they vary greatly, many of them having small 

 creeping stems, which seem to crawl upon the ground among the dead 

 branches of the surrounding trees, with whose gray colour their deep 



green shoots form a singular contrast. Others rise like candelabra 

 with many angular ascending arms, while a few elevate their tall and 

 deeply-channeled leafless trunks far above the stunted vegetation of 

 the sterile regions they inhabit, reaching sometimes the height of 30 

 or 40 feet. 



To enable them to endure the excessive drought to which they are 

 naturally exposed they are furnished with an unusually tough skin, 

 the evaporating pores or stomates of which are few in number and 

 very often to all appearance merely rudimentary. This contrivance 

 prevents their losing the scanty moisture which they collect from the 

 burning soil, and enables them to sustain the full ardour of the 

 brightest equinoctial sun without inconvenience ; in this respect 

 resembling the succulent fruits of Europe, such as the plum, the 

 grape, the peach, &c., which by the absence of stomates from their 

 tough skin are equally enabled to bear the powerful action of the 

 bright sun that is necessary for their maturation. 



These facts teach us what the points are that it is most necessary 

 to attend to in the cultivation of the numerous species which now 

 abound in our gardens. Their skin is so formed that perspiration 

 takes place very slowly through it, unless under the influence of 

 powerful stimulants and when in a young state. It is therefore 

 obvious that they should be sparingly watered or not watered at all 

 during a considerable period of the year. Dry as the places usually 

 are in which Cacti naturally grow, they are periodically visited by 

 heavy rains, which, combined with a bright light and a high tempera- 

 ture, force into activity even the sluggish vital powers of such plants 

 as those under consideration. At such a time the annual growth of 

 a Cactus takes place, secretions which enable the species subsequently 

 to form its flowers are deposited, and a general impulse is given to 

 all the torpid energies of its constitution. But by degrees the rains 

 moderate and finally cease ; the young cuticle which at its first for- 

 mation perspired freely becomes thicker and tougher, and impermeable 

 to moisture ; what food has been obtained during the short period of 

 growth is securely inclosed within the recesses of the stem ; and when 

 the air and earth become dry the plant is provided with the means 

 of enduring another long period of fasting and inactivity. With the 

 fall of rain the heat moderates, but the light to which the Cacti are 

 exposed is but little if at all diminished; so that the assimilation 

 and alteration of the food contained within the stem keeps continually 

 going on, however slowly. It is by following this natural course of 

 events that gardeners have succeeded in bringing their Cacti to that 

 extraordinary state of beauty for which they are now conspicuous ; it 

 is by attending practically to such points in the habits of the species 

 that we obtain the myriads of large, brilliant, red, or blush or snow- 

 white blossoms that form the glory of our green-houses in the spring. 

 A Cactut is placed in a damp stove, exposed to all the light that can 

 be collected without being concentrated, and it begins to grow : it is 

 then watered, at first gently, afterwards copiously with water holding 

 a quantity of organisable matter (manure) in solution ; this practice 

 is continued for three months, when the quantity of moisture is 

 diminished and the temperature is lowered, but exposure to light is 

 still attended to, till at last the plant sinks to rest. In this state it 

 is kept till the season for again forcing it into growth shall have 

 returned, when it is subjected to a repetition of the same treatment 

 as before. 



If the Cactaceee are to be propagated, their branches or joints, if 

 they have any, are cut off, a little dried, and then placed in a hot and 

 damp place, when they strike root immediately. Among the practi- 

 cal consequences, De Candolle observes, that result from the facility 

 with which they are thus multiplied, is one which deserves to be 

 noticed on account of its importance, namely, the manner in which 

 the Opuntia is employed to fertilise the old lavas at the foot of ^Etna. 

 As soon as a fissure is perceived, a branch or joint of an (Opuntia is 

 stuck in : the latter pushes out roots, which are nourished by the 

 rain that collects round them, or by whatever dust or remains of 

 organic matter may have collected into a little soil : these roots, once 

 developed, insinuate themselves into the most minute crevices, expand, 

 and finally break up the lava into mere fragments. Opuntias treated 

 in this manner produce a great deal of fruit, which is sold as a refresh- 

 ing food throughout all the towns of Sicily. 



Where however the species have neither branches nor joints, as is 

 the case with some of the species of Mclocactus and Echinocactus, a 

 different mode of propagation is had recourse to : it is then necessary 

 to compel them to branch by artificial means. Each of the numerous 

 tufts of spines that occupy the ridges of their stems is a bud, and is 

 capable of being forced into a branch, if by any means the general 

 tendency to grow at the upper extremity only is checked. This is 

 effected either by burning the apex of the plant with a broad flat iron, 

 or by cutting the plant across below the top, in either of which cases 

 several of the spiny buds will gradually swell and develop themselves 

 aa little branches, which being broken off will strike root and become 

 new plants. 



It is on species of the Cactacea; that the cochineal insect feeds. Of 

 these the most common are the three following : Opuntia Tuna, which 

 seems the most employed in Peru ; 0. Hernandezii, which is the most 

 celebrated in Mexico ; and 0. cochenilli/era, the native province of 

 which is somewhat doubtful. 



CACTUS, a genus of plants, the type of the natural order Caclacece. 



