The family of Aroideæ is there represented by the Pothos, whose fleshy and herbaceous stems are surmounted by leaves sometimes arrow-headed, sometimes digitate or elongated, and always divided by thick cord-like nerves. We know that the Aroideæ alone possess, in the vegetable kingdom, the property of disengaging, while flowering, a heat appreciable by the thermometer. To this family belong the Caladiums, a genus closely allied to the Pothos. With these lianas mingle the branching stems of the Passifloræ, or Passion-Flowers, so named because Pierre de Ceza, in his “Histoire du Pérou,” asserted that he had recognized in the fantastic flowers of this genus of plants all the instruments of our Saviour’s Passion—an idea which could only have been conceived by an imaginative and credulous Spaniard. Elsewhere the Bignonias open by hundreds their large and richly-coloured flowers; the Bauhinias stretch along the trees their long leafless branches, often 40 to 45 feet in length, which sometimes hang vertically from the lofty summits of the Swietenias, or Mahogany trees, and sometimes extend obliquely from one huge trunk to another, like the ropes of a ship. The Tiger-Cats, says Humboldt, display a wonderful agility in mounting or descending these graceful vegetable shrouds.
Upon the umbrageous banks of the Rio Magdalena grows a creeping Aristolochus, whose flowers in their extraordinary development surpass those of the Rafflesia Arnoldi, measuring often three feet and a half in circumference. The forests of which we are now speaking also nourish numerous species of Convolvulus; I may particularize the Convolvulus batatas, a climbing plant, whose roots produce the feculent and saccharine tubercules known over the wide world by the name of “Patates,” and frequently but erroneously confounded with that most useful vegetable, the Potato. The root of another Convolvulus, a native of Mexico, constitutes the Jalap officinalis, which figures in the veterinary pharmacopœia as an important purgative.
Certain lianas, common enough in the South American forests, belong to the family of Sapindaceæ, which, like the orders Loganiceæ and Euphorbiaceæ, owe their reputation chiefly to the medicinal or poisonous substances extracted from them. Among the Sapindaceæ I shall mention only the genus Paullinia, which includes several species endowed with narcotic properties. These properties appear especially developed in the Paullinia pinnata. Its bark, leaves, and fruit contain an abundant acrid principle with which the Indians of Brazil prepare a slow but certain poison. The Indians of Guiana extract from the Paullinia cururu another substance with which they envenom their arrows, and which was long supposed to be the veritable Wourali. But Sir Richard Schomburgk has shown that the latter formidable poison is really extracted, as I have already recorded, from the Strychnos toxifera, a shrub of the family Loganiaceæ, which flourishes in Guiana and Brazil. To the same family and the same countries belong the Ignatia amara, whose seeds are known by the name of “St. Ignatius’ Beans.” These beans contain two alkaloids, Strychnine and Brucine, which we also extract from the Nux vomica, and which must be classed among the most violent poisons known to the toxicologist.
While speaking of the poisonous plants of South America, a few words in reference to the Manchineal (Hippomane Mancenilla) will not be inappropriate. This tree thrives best, it is said, on the sea-shore. It bears a profusion of very pretty fruit, resembling in colour and form the Red Apple (the Spanish Manzanilla), and exhaling an agreeable, lemon-like odour. They are, therefore, scarcely less beguiling than Dead Sea fruits; but they are also very poisonous, yet less deadly than the milky juice which flows from the slightest incision made in the tree’s thick and grayish bark. This juice, received into the stomach, or introduced into the blood through a wound, slays the victim with awful quickness. If it do but touch the skin, it excites a violent irritation, and raises swellings or boils of the worst description. The very vapour which it emits causes a painful itching in the eyes, the lips, and the nostrils. It was formerly asserted that to sleep under the shade of a Manchineal tree was certain death; but the naturalist Jacquin, in the interests of science, courageously made the experiment, and proved the falsity of the story.
The Manchineal is not unfrequently confounded with other poisonous Euphorbiaceæ, as the Sapium aucuparium and the Excœcaria agallochia, which flourish in very nearly the same regions. The Excœcaria, it is said, is not less dangerous than the Manchineal. It owes its name (ex, and cœcus, “blind”) to the circumstance (or the fable) that some European sailors, while felling wood in the forest, having accidentally struck with their axe a tree of this species, were blinded by the milky juice which sprang into their eyes.
By a kind of compensation, the Tropical Forests, which contain so many poisonous plants, produce also a great number of the highest utility to man. Some offer him efficient remedies against the diseases which beset his frame; others nourish him with the fecula of their roots or the delicious substance of their fruits; others again supply him with textile fibres, dyeing or resinous materials, and woods which the artist and the artisan convert to numerous uses. This vegetable wealth has been widely distributed over South America. It will suffice to indicate a few of its more notable sources.
If we direct our attention to medicinal plants, we shall probably find none more precious than the Quinquina, whose bark is the most effective of all febrifuges, and which is endowed, moreover, with very valuable tonic and depuratory properties. Sir Samuel Baker, in his recent address to the British Association at Dundee, pronounced it the traveller’s best friend, the powerful weapon with which he could securely enter the African wilderness, and successfully contend against its demon-host of fevers and agues. The Quinquinas (genus, Cinchona; family, Rubiaceæ) are trees or evergreen shrubs with large and handsome leaves, and flowers whose form and fragrance remind one of the lilac. They are diffused over the two slopes, but chiefly along the eastern slope, of the Andean Cordilleras, in the republics of Venezuela, New Granada, Ecuador, Peru, and Bolivia. The traveller meets them occasionally in picturesque groups or thickets which the Peruvians call Manchas (spots); but they are more frequently scattered in immense forests.
What of the lactiferous and resinous plants? South America is the native land of the trees whence we extract the resinous gums called “Animé d’Amérique,” “White Amber,” and “Soft Brazilian Copal,” and the “Hevea Guyanensis,” which furnishes the greater portion of the caoutchouc imported into Europe.
Caoutchouc was described for the first time in 1736, by the scientific travellers Bouguer and La Condamine, members of a Commission despatched to Peru by the Parisian “Académie des Sciences,” to measure an arc of the meridian. A few years later, the engineer Fresneau, who resided for a long time in Guiana, collected, with the assistance of a native, ample information in reference to caoutchouc and the tree which produced it. Finally, in 1768, was found in a work by the traveller Aublet on the Flora of Guiana, the description and figure of the Hevea. This tree attains a height of 50 to 70 feet. The almond enclosed in the kernels of its fruits is white, of a very agreeable taste, and much esteemed by the Indians, who also extract from it an oil for seasoning their food.
The Banana, the American Agave, the Bamboo, and divers Palm-trees supply the inhabitants of South America with suitable materials for the fabrication of various tissues, from the finest and most brilliant linen cloth to the rude mats which ornament the cabin of the savage. Trees bearing fruits or edible roots are innumerable. To the Bananas and Cocoa-trees which I have already mentioned, we may add, as the most useful, the Maranteas or Canneas, especially the Maranta arundinacea, M. alloya, and M. nobilis, whose roots, rasped and washed, constitute the popular and valuable farina so widely known as Arrow-root; the Guavas (Psidium pyriferum, and P. pomiferum), whose gilded fruits contain a succulent and perfumed pulp; the Papaw tree (Carica papaya), resembling the Palm in its port and aspect, and also loaded with large yellowish fruit, whose flesh is exceedingly savoury and aromatic. The Papaw, moreover, enjoys some extremely remarkable properties; thus, its milky juice exhales, when burnt, an ammoniacal odour, and chemical analysis has recognized therein the presence of fibrine. Mix some of this juice in water, plunge into the mixture fresh hard meat, and in a few moments it will become exquisitely tender. The very exhalations of the tree operate in the same manner, and the inhabitants of the regions where it flourishes suspend to its branches such meat and poultry as they wish to soften.