8, Stamens. 9-12 Enne-Dodecandrous. Hypogynous.

N.B.-In the pistillate flowers there are two filaments, but no anthers.

Most of the British species of the Order belong to a distinct type, the genus Spurge (Euphorbia), characterised

by achlamydeous, monoecious flowers. The staminate flowers are monandrous, and the ovary of the pistillate flower consists of 3 carpels. One pistillate and several staminate flowers are collected within a small involucre, bordered by marginal "glands," which may be mistaken by beginners for petals or calyx-lobes. A joint some

distance below the anther of each staminate flower indicates the point where the filament joins the pedicel. At

this node, in an allied genus, a partial perianth is developed.

FIG. 141-Involucre of Spurge, bordered by four horned "glands," and containing numerous male flowers and one female. The pedicel of the latter is curved over the side of the involucre.

OBSERVE the milky juice of the Spurges (Euphorbia), which is dangerously poisonous in some species, and is

used by barbarous African tribes to poison their weapons. The milk of a species of Hevea, Brazilian trees, yields the best Caoutchouc exported from Para. It flows from wounds in the bark, and is allowed to dry over moulds of clay, the clay being washed out when the "India-rubber" is sufficiently stiffened. Upwards of 264,000 cwts. of Caoutchouc were imported into the United Kingdom in 1890. It must be borne in mind, however, that this product is afforded by several other plants besides Siphonia: especially by a species of Fig (Ficus) in India.

Gutta-percha is the similar product of an Indian tree belonging to an Order (Sapotaceae) not represented in

Britain. Upwards of 70,000 cwts. of Gutta-percha were imported in 1890.

Cassava, or Mandiocca Meal, an important article of food in the Tropics, especially of South America, is afforded by species of Manihot. The juice of one of the Cassava-producing species (M. utilissima) is a virulent poison: this is removed from the root by washing, after it has been grated. Tapioca is the fine starch which settles down from the water used to wash Cassava. It is granulated upon hot plates. The roots of the Bitter Cassava weigh from 30 lbs. to 40 lbs., and the crop is

said to be one of the most productive yielded by any food-plant.

Several species afford important drugs, as Castor Oil, obtained from the seeds of Ricinus, and Croton Oil, from the seeds of Croton Tiglium. African Teak (Oldfieldia) and the Box (Buxus) yield valuable wood; the latter furnishing the blocks used by wood-engravers, for whose purposes its close texture and hardness eminently fit it. It is native in South and South-Eastern Europe, and grows in some wild situations in England, but it may have been introduced long ago to the latter.

56. Natural Order-Urticaceæ. The Nettle Family. DISTRIBUTION.-Cosmopolitan, but most numerous between the Tropics.-British genera 3, species 5. Stinging herbs. Flowers unisexual. Ovary I-celled, with I

erect ovule.

Type-Small Nettle (Urtica urens).

An annual herb, with opposite simple leaves, stinging hairs, and axillary clusters or spikes of small monœcious flowers.

OBSERVE the stamens opposite to the leaves of the perianth, and their elastic filaments, flying back when released by the expansion of the flower.

The bark of some species of the Nettle Family affords an invaluable fibre, especially that of the Hemp-plant Cannabis sativa), which has been cultivated from a remote period, in temperate climates, for its fibre. It is recorded as having been under culture 2,500 years ago. The fibre is obtained in the same way as Flax. In India, Hemp is

grown chiefly for the sake of a narcotic, intoxicating gumresin, called Churras, exuded by the leaves and stem. The dried leaves and twigs are smoked.

FIG. 146.-Longitudinal section of fruit of Small Nettle.

FIG. 147.--Section of seed of same showing the large embryo, with a superior radicle and but little albumen.

Chinese Grass-cloth fibre is yielded by a stingless Nettle of Eastern Asia (Boehmeria nivea).

The Hop (Humulus Lupulus) is remarkable amongst the Nettle Family for its twining stem. The bracts of the inflorescence become enlarged under cultivation and covered with minute glands, containing a bitter gum-resin