Cephalium
Cephalia ( Gr. Κεφαλή kephalē "head") are conspicuous inflorescence zones that are formed by some cactus plants. They occur only in relatively few genera and are then typical for these genera. Cacti that develop cephalias bloom exclusively in these separated zones. The advantages of combining flowers in a cephalium over single flowers are both better protection of flowers and fruits and greater visual stimulus for pollinators.
In terms of development history, four different forms can be distinguished.
- Pseudocephalies ("false cephalias") are areas with increased hair formation on areoles of otherwise morphologically normal shoots . They occur, for example, in individual species of the genera Cereus and Cleistocactus .
- Real cephalias are areas with strongly increased wool and bristle formation not only of the areoles, but also of the surrounding epidermis . In extreme cases, all epidermal cells of the cephalium are transformed into trichomes .
- Split cephalias arise laterally and are typically sunk into the shoot axes in the shape of a gap or channel. They usually occur on one side, sometimes on several sides, or can seldom enclose the entire stem axis in a jacket-like manner. However, this does not restrict the length growth of the rung. Fissure cephalia are typical of the genera Cephalocereus , Coleocephalocereus , Espostoa , Facheiroa , Micranthocereus , Pachycereus , Pilosocereus and Stephanocereus .
- In the genus Arrojadoa , the cephalias are formed at the end of each growing season, but then grow through in the new growing season. In this way they form rings that document the annual growth of the rung.
- In the genera Melocactus and Discocactus , the cephala are formed at the end, but not grown through, and thus limit the growth in length of the plant body. The cephala are strongly separated from the plant bodies, mostly much thinner than these, in Discocactus rather small and flat, in Melocactus up to about 50 cm high.
literature
- Franz Buxbaum : Morphology of the "Spaltcephaliums" from Espostoa sericata : In: Austrian Botanical Journal . Volume 99, number 1, 1952, pp. 89-99, doi : 10.1007 / BF01288567 .
- Franz Buxbaum: The hairy cephalic carriers of South America . In: Austrian Botanical Journal . Volume 106, number 1/2, 1959, pp. 138-158, doi : 10.1007 / BF01279003 .
Web links
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