Lastly, in this connexion may be mentioned the very interesting and beautiful group of orchids (Orchidaceæ), many of which live high up in the air, supported on the branches of trees, from which their roots hang freely down. Such orchids are sometimes spoken of as "air-plants."
All the Angiosperms as yet mentioned, from the grasses to the orchids inclusively, belong to the lower of the two great groups or classes into which, as was lately said, the whole mass of Angiosperms is divided.
This great group is named Monocotyledones (on account of the structure of the seed), and it is sometimes spoken of as Endogens, in reference to a generally prevalent habit of growth. The members of this whole class will then hereinafter be spoken of as "Monocotyledons."
All the plants which yet remain to be enumerated belong to the other and still greater group of Angiosperms called (also in reference to their seeds) Dicotyledons, a group sometimes spoken of as "Exogens," in reference to the habit of growth prevalent amongst its species.
All our familiar trees which are not conifers, and most of our flowering shrubs and herbs, are "Dicotyledons."
Amongst the many orders which compose the Dicotyledonous group the few following may be selected for enumeration, either on account of the general interest they possess, or because they will have to be more or less referred to hereafter.
We may thus note the singular order of vegetable parasites, the Loranthaceæ, an order containing some thirty genera with four hundred species, and including the mistletoe, which is traditionally venerable in our island. The great group of catkin-bearing trees (Amentaceæ), contains a great assemblage of plants, familiar in England, such as the hornbeam, hazel, oak, beech, Spanish chestnut, birch, willow, poplar, &c.[24]
The largest and one of the most remarkable flowers in the world, Rafflesia—a parasite found in Java and Sumatra by Sir Stamford Raffles—is the type of the small order Rafflesiaceæ. The eccentric pitcher-bearing plants form the order Nepenthaceæ. The English herb called "Spurge" (with its milky juice), belongs to the order (Euphorbiaceæ), which is a large[25] cosmopolitan group, some species of the plants belonging to which attain, in hot countries, the size of trees. Certain African species strangely resemble different kinds of Cactus. The elm order (Ulmaceæ) may come next. The hop, the hemp, the mulberry, the fig, and the dorstenia are all nearly allied, the first two belonging to the order Cannabinaceæ, the last three to the Moraceæ. The bread-fruit of the South-Sea Islands belongs to the same order (Artocarpaceæ) as does the deadly upas-tree of Java. Garments made of the inner bark of this plant are like the shirt of Nessus, and will produce intolerable irritation; and even climbing the tree to obtain its flowers is said to have produced severe effects on the climber. In proximity to the last-mentioned plant comes appropriately (as also in its proper botanical order) the group of stinging-nettles (Urticaceæ). The curious Australian plants which delighted the eyes of Captain Cook's botanical companions belong to the order Proteaceæ. Besides these may be mentioned the dead-nettle order (Labiatæ); the broom-rapes (Orobanchaceæ); the order of snap-dragons and foxgloves (Scrophularineæ); the potato group (Solanaceæ), which includes the deadly nightshade and the dulcamara of our hedges; the parasitic order (Cuscutaceæ); the beautiful group of convolvuluses (Convolvulaceæ); the gentians (Gentianaceæ); the primrose group (Primulaceæ); the heaths (Ericaceæ); the graceful hair-bell and its allies (Campanulaceæ); the very large group to which belong the daisy, dandelion, and thistle (Compositæ); the honeysuckle order (Caprifoliaceæ); the ivy (Araliaceæ); the large order containing the fennel, hemlock, and a multitude of other forms which, though mostly ranking as herbs, attain gigantic dimensions in some species found in Africa and Kamskatka (Umbelliferæ); the very singularly-shaped group of cactuses (Cactaceæ), with leafless fleshy stems, which sometimes look like dry columns and sometimes are globular; the begonias (Begoniaceæ); the cucumbers, melons, and vegetable marrows (Cucurbitaceæ); the singularly-formed passion-flowers (Passifloraceæ); the myrtles (Myrtaceæ); the carnivorous group containing the sundew and Venus's flytrap (Droseracæ); the fleshy houseleek and stonecrops (Crassulaceæ); the Saxifrages (Saxifragaceæ); the rose group (Rosaceæ), which includes within it most of our fruits, such as the apple, pear, strawberry, cherry, peach, plum, almond, and others; the very large order which contains the peas, beans, and their allies (Leguminoseæ); the horse-chestnut order (Hippocastaneæ); the maples (Acerineæ); the hollies (Ilicineæ); the oranges and citrons (Aurantiaceæ); the cranesbills and pelargoniums (Geraniaceæ); the flaxes (Linaceæ); the limes (Tiliaceæ), in which the useful jute is included; the mallows (Malvaceæ); the St. John's worts (Hypericaceæ); the order of pinks (Caryophylleæ); the pansies (Violaceæ); the rock-roses (Cistaceæ); the mignonette group (Resedaceæ); the great wall-flower and cabbage group (Cruciferæ); the poppies (Papaveraceæ); the water-lilies (Nymphaceæ); the berberries (Berberideæ); the custard-apples (Anonaceæ); the magnolias (Magnoliaceæ); and, finally, the great group (Ranunculaceæ) containing the anemones, the clematis, hellebore, monkshood, and the buttercup, which last is of great use to the student of Botany because it is an excellent type of all flowers.
The above may serve as a brief enumeration of the more generally known or more interesting orders of flowering plants, as also of the most noteworthy forms of cryptogams. The much more numerous and complex groups of animals have also been catalogued in the earlier and larger part of this Essay, which may thus, it is hoped, answer the purpose of an introduction to those multitudinous forms of organic life, the leading points in the structure and functions of which are hereafter to occupy us.
The main groups of Animals and Plants may be provisionally tabulated as follows:—