Flora of New Zealand Series

Prostrate to erect or stemless annual to perennial usually succulent herbs or shrubs. Lvs usually opposite, rarely alternate, stipulate or exstipulate, fleshy, terete to trigonous or flat, usually smooth or papillate, rarely pubescent or lepidote; papillae sometimes glittering. Fls solitary or in loose cymes. Sepals (3)-4-6-(8), unequal, rarely equal. Petals many or rarely 0, brightly coloured, in 1-several series, free or very shortly fused at base. Staminodes present or 0. Stamens usually many, rarely 1 or few. Ovary usually inferior, rarely 1/2-inferior to superior, 2-5-(16)-locular; placentation axile to parietal; ovules numerous. Stigmas free, as many as locules. Fr. usually a multicelled capsule opening when wet by as many winged or unwinged valves as the styles, by the action of 2 expanding keels on the inner surface of each; locules with or without a lid; each placenta with or without a distal tubercle, or tubercle 2-lobed; rarely the fr. indehiscent, mucilaginous, or a berry or nut or circumscissile capsule. Seeds numerous, ovoid, sometimes compressed, variously sculptured or smooth; embryo large, curved around mealy endosperm.

140 genera, 2300 spp., mostly in southern Africa, a few in E. Africa, Middle East, Mediterranean, California, Chile and Australasia.

Tribes Tetragonieae (60 spp.) and Mesembryanthemeae (2000 spp.), to which all the genera treated here belong, are sometimes treated as separate families, Tetragoniaceae and Mesembryanthemaceae. Trib. Mesembryanthemeae have distinctive fls and frs. The fls are usually very brightly coloured, especially the several ranks of petals which superficially resemble the ray florets of the Asteraceae or the petals of the Cactaceae. The fr. type is termed a hygrochastic capsule and is peculiar to the trib. Hygrochastic capsules open only when wet and close when dry by a pair of expanding keels attached to the inner surface of each valve. Each keel may or may not carry a wing and each septum of the capsule may or may not be extended apically into a lid which partly blocks the locule (Fig. 9). The physical attributes of hygrochastic capsules remain effective after death of the plant, and apparently limit seed dispersal to the times when heavy showers have made conditions suitable for germination and establishment.

A good illustrated reference to trib. Mesembryanthemeae is Herre, H., The Genera of Mesembryanthemaceae (1973). For a further key to genera see Rowley, G., Name that Succulent (1980). Jacobsen, H., Lexicon of Succulent Plants, part 2 (1974), provides brief descriptions of spp. but few keys. Identification of spp., particularly in the large genera Lampranthus, Ruschia, and Delosperma, is difficult.

Spp. of Mesembryanthemeae are widely cultivated in N.Z. and tend to become locally naturalised as garden escapes, particularly on sunny coastal sites. Other spp. may be locally established in N.Z., but not represented in herbaria.

Eight of the naturalised spp. of Aizoaceae are illustrated in Plate 6.

Fig. 9. Aizoaceae, hygrochastic capsules in open (wet) and closed (dry) states. A Aptenia cordifolia; B Disphyma australe; C Ruschia tumidula. © All rights reserved. [Image: 4X6I]