A member of the Arachnida, the class of arthropods that includes spiders, mites, scorpions, and ticks. Archetype

The wild ancestor of a modern cultivar. Areca catechu

This palm is the source of the betel nut, which is chewed as a narcotic by more people than use chewing gum. It is chewed as a 'quid' of betel pepper leaves with a dash of slaked lime. This 'quid' turns the saliva red and this colours walls and sidewalks from spitting. The young palm is also a popular house-plant. There is some scope for amateur breeders to select superior palms within existing populations in areca-producing countries. Areca palm

See: Areca catechu. Armillaria

Armillaria mellea is known as the honey fungus, and it can cause a serous disease of many species of tree. It produces long black rhizomorphs that look like boot-laces, and that can grow through the soil and spread the disease from tree to tree. Armillaria often produces toadstools on dead tree stumps. In the tropics, it occurs only at high altitudes. It has even been postulated that a large network of rhizomorphs constitutes the largest living organism. Foresters often ring-bark trees about a year before felling them, and this denudes the roots of nutrients. The fungus is the unable to invade them. Another defence is to dig trenches that the rhizomorphs cannot cross. However, many pathologists think that Armillaria will only attack trees that are weakened from some other cause such as water-logging or shallow soil. It is not feasible for amateurs to breed for horizontal resistance to this disease. Armoracia rusticana

Horse radish. The roots are used to make a peppery condiment, but this species does not flower or set seed. It is definitely not recommended for amateur plant breeders. There are many clones with widely varying degrees of pungency. These ancient clones have few pests or disease and they are a good example of both the effectiveness and the durability of horizontal resistance.

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