Fig. 470.—Flowers (after the removal of the petals).
7. Aurantieæ, Orange Group. Fruit a berry with a leathery external layer.—The most typical flower is found for example in Limonia: S5, P5, A5 + 5, G5 (2–5).—Citrus has 4–5–8-merous flowers, a gamosepalous, dentate calyx, free petals, one whorl of stamens which are split irregularly into several bundles (Fig. [470]). The fruit is a multilocular berry provided with a thick, tough, outer layer. The juicy pulp, which fills up the loculi and envelopes the seeds, is formed from many large-celled, juicy hair-structures which arise on the inner side of the walls of the loculi and by degrees entirely fill them up; the dissepiments remain thin, and form the partitions so easily separating from each other (Fig. [469]). The seeds in many instances are remarkable for containing several embryos. The blade of the leaf is separated from the frequently winged stalk by a node (and hence is a compound leaf with only the terminal leaflet developed?) (Fig. [468]); in other genera, as Triphasia, there is a fully developed trifoliate leaf. Thorns are frequently developed.—The species of this genus, which is a native of the warmer parts of S. E. Asia, are very hard to separate. The differences are found in the forms of the fruit, the leaves and the leaf-stalks, and in the number of stamens. Citrus medica, “Cedrat” (Ind.); C. limonum, “Citron,” “Lemon” (introduced into Italy in the 3rd to 4th century). Officinal: the fruits and essential oil of Lemon. C. aurantium from E. Asia, the Orange (introduced into Italy in the 14th century). C. vulgaris (Fig. [468]), Bitter Orange (introduced into Europe at the time of the Crusades); the unripe Bitter Oranges, and peel of the Bitter Orange is officinal; it is from the flowers of this species especially that the essence of Neroli is made. C. limetta, C. bergamia, Bergamot; essence of Bergamot is officinal. C. decumana, Pomalo, a native of the Islands of the Pacific. About 780 species; chiefly tropical.
Order 4. Burseraceæ. Fruit a drupe; 1–5 stones. The bark, as well as the other parts, contain strong aromatic resins and balsams, and hence several species are used: the Myrrh tree, Commiphora (Balsamodendron) from Arabia and Africa; Officinal: Myrrha (Commiphora myrrha). Mecca-balsam from C. opobalsamum, Arabia; E. Africa. The Incense-tree (Boswellia) from the same parts of the globe and E. India. The incense of B. carteri is medicinal (Frankincense). The resin (Elemi) of Protium-species is officinal, and is used technically for varnish (S. Am.). Takamahaka-resin from Elaphrium (S. Am.) Protium (Icica); Amyris (1 carpel). 270 species; tropical.
Order 5. Zygophyllaceæ. The majority have opposite, pinnate leaves with stipules. Leaves without pellucid dots. The filaments have a scale on the inner side. The most important is Guaiacum officinale (West India), the wood (Lignum Vitæ) of which is very hard and heavy, this wood and Gum-guaiacum are officinal. Others have a peculiar repulsive smell and taste: the Creosote shrub (Larrea mexicana) and Zygophyllum simplex. Tribulus terrester is a common weed in S. Europe. Fagonia. Peganum harmala (South of Russia) yields a red dye.—110 species; especially in the Tropics; several species in sandy deserts. Nitraria.
Order 6. Simarubaceæ. This order is distinguished by the abundance of bitter substances which it contains (Quassine) especially in the bark and the wood. The wood of Quassia amara (Guiana, Antilles) is officinal; Picraena excelsa yields Jamaica Quassia; the bark of Simaruba, Simaba-species and others is used. Ailanthus glandulosa is a garden plant (pinnate leaves, winged fruit).—110 species. Tropical.
Order 7. Ochnaceæ. Flowers diplostemonous, 5-merous. The unilocular ovaries, which are individually free, project considerably into the air around the gynobasic style; 1 ovule in each loculus; the fruitlets are drupes. Shrubs; leaves alternate, with stipules. Ochna; Ouratea.—160 species; tropical; especially American.
Order 8. Anacardiaceæ. The ovary rarely contains more than 1 ovule, even though there be several loculi and several carpels; in Anacardium all the 10 stamens except one become suppressed. Resin passages.—Anacardium. The most peculiar feature is the development of the flower-stalk into a fleshy body about the form and size of a pear (A. occidentale from Trop. Am. and A. orientale from E. Ind.) which bears the kidney-shaped nut (the so-called “Cashew-nut”) on its apex. Mangifera indica (the Mango-tree, from E. Ind.) is cultivated in several tropical countries on account of its delicious drupe. Similarly, species of Spondias (S. dulcis, Pacific Islands, S. lutea). Several species of Rhus are ornamental shrubs in this country, for instance, R. typhina (N. Am.), R. cotinus (the Wig-tree, the barren flower-stalks of the panicles being feather-like and hairy); R. toxicodendron (Poisonous Sumach, from N. Am.) is poisonous. Chinese galls are produced by the sting of a leaf-louse (Aphis chinensis) on R. semialata (China), and Japanese wax is from the seeds of R. succedanea (Japan). Considerable quantities of Sumach (R. coriaria) are used in tanning and as a black dye. Officinal: the mastic resin of Pistacia lentiscus (the Mastic-tree, from the Mediterranean). The fruits of Pistacia vera (Syria) are edible; P. terebinthus and others yield turpentine.—450 species; tropical.
Order 9. Icacinaceæ. Flowers 4–5-merous; haplostemonous; receptacle convex or cup-like surrounding the gynœceum; in the (single) loculus of the ovary, 2 anatropous, pendulous ovules.—200 species; tropical.