AIZOACEAE

The tribe Ficoideae in the family of Aizoaceae comprises about 120 genera, with several hundred species and varieties. They are better known as Mesembryanthemums , of which the greater number are natives of South Africa.

They are roughly divided into three categories: species with elongated stems, erect or prostrate; low-growing species; species that have, been called “mimicry plants” because it has been observed how cleverly these plants match their surroundings in their native habitats.

They are found in regions notorious for long periods of drought, and in order to succeed in the struggle for life, the plants have been constructed to retain and hold moisture for as long as possible, and to protect themselves in various ways against excessive evaporation. This protection is achieved by: (I) A reduction of the leaf surface resulting in a re-duction in the number of stomata or breathing pores. (2) A thickening of the epidermis or skin, so that the stomata lie deep below the surface. (3) A covering of hairs or wax to prevent the stomata being dried up by the burning heat. (4) The removal of the stomata to a part of the plant which is not exposed to the direct action of the sun s rays (mimicry plants).

Certain of the Ficoideae referred to as mimicry plants have a most remarkable structure of leaf tops which permits the light to penetrate down to the assimilating tissue, which would otherwise be deprived of all light, for in nature they grow buried in the soil, the upper surface only showing. Plants having these windowed leaves are found among the following genera: Lithops, Fenestraria, Frithia, and Conophytum.

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