and ground to form Cocoa. Finely ground, made up into a paste and flavoured, they form Chocolate. In 1877 nearly

FIG. 97-Cocoa and Chocolate Tree (Theobroma cacao). Much
reduced.

seventeen millions of pounds of Cocoa were imported into Great Britain; upwards of ten millions being entered for home

use.

15. Natural Order-Geraniaceæ. Family.

The Crane's-bill

DISTRIBUTION.-Temperate and sub-tropical regions of both hemispheres; two genera being largely developed at the Cape of Good Hope.-British genera 4, species 19. Herbs. Flowers regular or irregular. Stamens definite, free or monadelphous. Placentas axile.

Type-Meadow Crane's-bill (Geranium pratense).

A perennial herb, with multipartite stipulate leaves, blue pedunculate regular flowers, and beaked fruits.

OBSERVE 5 stamens alternately shorter than the rest ; in the allied genus Erodium (Stork's-bill) these are without anthers the beak-like prolongation of the consolidated apices of the carpels. After flowering, this beak grows out to a length sometimes of 2 or 3 inches.

Compare the slightly irregular flower of a Garden Geranium (Pelargonium) with the irregular flower of Indian Cress (Tropæolum majus). In both the calyx is spurred, the spur being free in the latter and adnate to the pedicel in the former; as may be seen on making a cross-section of the pedicel, immediately under the flower.

Cultivated varieties of two or three species of Cape Pelargonium are universal favourites, as are also Indian Cress (Tropaeolum majus) called Garden Nasturtium (but not to be confounded with true Nasturtium, the Watercress, belonging to the Crucifers) and the Canary-flower (T. peregrinum),

Wood-sorrel (Oxalis Acetosella), with compound trifoliolate leaves, belongs to the same Natural Order. It affords an example of remarkable dimorphism in the flowers, similar to that presented by Sweet Violet (page 127).

Some species, as Pelargonium triste and Oxalis tuberosa, have tuberous roots, which are used as food.

16. Natural Order-Polygalaceæ.

Family.

The Milkwort

DISTRIBUTION.-Temperate and tropical regions in both hemispheres. One British genus, species 2.

Herbs. Flowers irregular. Stamens 8, monadelphous.

Type-Common Milkwort (Polygala vulgaris). A low wiry perennial herb, with alternate entire leaves, and racemose irregular flowers.

OBSERVE the two large lateral inner sepals, called wings, which persist and inclose the fruit: the cohesion of the filaments and their adhesion to the petals, so that the latter appear to form a gamopetalous corolla: the I-celled anthers, dehiscing by pores: the membranous hood of the stigma, apparently designed to insure selffertilization. Actual fertilization, however, takes place through the agency of bees, which thrust their probosces down to the honey-gland at the base of the flower, and on their withdrawal leave pollen, which they may have imported, upon the short projecting stigmatic hook in front of the spoon-shaped hood.

17. Natural Order-Acerineæ. The Maple Family (a Tribe of the Tropical Order Sapindacea).

DISTRIBUTION.-Chiefly restricted to the North temperate zone of both hemispheres.-One British genus, species 2.

Trees. Leaves opposite. Stamens definite.

Type-Common Maple (Acer campestre).

A dark-green deciduous tree, with opposite 5-lobed leaves, and loose corymbose flowers.

The number of parts in the floral whorls is variable. OBSERVE the large hypogynous disk, and the winged fruit, called a samara.

Some species of Maple abound in a sweet juice, which is collected from the North American Sugar Maple (A. saccharinum), and boiled down into Maple sugar. The sap is obtained in spring by tapping the tree to a depth of about half an inch, and inserting a tube. The sap flows for six weeks at from two to three gallons per day. Good Maples yield an average of four pounds of sugar each season.

The soft white wood of the Sycamore is used for trenchers, bowls, &c. Maples are often incorrectly called Plane Trees.

The Horse Chestnut (Æsculus) is an Asiatic tree, commonly planted in England for shade, belonging to another tribe of the Natural Order Sapindaceæ.

OBSERVE the structure of the embryo of the exalbuminous seed of Horse Chestnut, the cotyledons being more or less connate, so that the seed looks as though it were

acotyledonous. Compare also the seed of Horse Chestnut with the fruit of the Sweet Chestnut (Castanea). They resemble each other closely at first sight, but the coat of the latter is a perianth, adherent to an inferior ovary. The bitter flavour of Horse Chestnut seeds is said to be corrected by adding one or two per cent. of carbonate of soda to the ground meal, and washing it until it becomes white. From 100 lbs. of the Chestnuts 60 lbs. of meal or flour may be obtained.

Division. Calyciflora.

18. Natural Order-Celastraceæ. The Celastrus Family. DISTRIBUTION.-Dispersed throughout the tropical and temperate zones.-One British genus, species 1. Type-Common Spindle tree (Euonymus europæus). A deciduous glabrous shrub, with opposite undivided leaves, and small yellowish-green cymose flowers. (The only British species.)

OBSERVE the bright orange-coloured arillus, covering the seed. The arillus is a cellular investment growing more or less over the seed as it matures, either from the funicle (the pedicel by which the ovule is attached to the placenta) or from the micropyle. In the Nutmeg fruit we have another good example of the arillus in the mace which closely invests the crustaceous testa enclosing the Nutmeg." The Nutmeg is farther remarkable from its interrupted, marbled albumen; such albumen is termed