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Macrocentra - with a large central spine.
Macromeris - with long or large divisions.
Macrorhiza - with long or large roots.
Macrozamin - a toxic glycoside - methylazoxymethanol-ß-primeveroside - found only in Cycads.
Structure of Macrozamin
Macula - a spot or blotch. Hence Adj. maculate = with spots or blotches.
Maguey - the Agave or century plant, especially A. americana but includes several other species. Also applied to cordage and fabrics made from fibres of the Maguey plant.
MAM - a neurotoxin - methylazoxymethanol - found exclusively in Cycads as its glycosides as e.g. Cycasin, Macrozamin and related compounds. MAM is released from the glycosides by enzymatic processing in intestinal bacteria. Hence the glycosides are only toxic after ingestion.
Structure of methylazoxymethanol
Mamilla - nipple-shaped tubercle with an areole at its tip.
Mamillate - with breast or nipple shaped projections.
Margin - the edge of a leaf or other organ.
Marginal - along the margin or edge.
Marine - of the sea or saline water.
Maritime - of the sea, coastal.
Marsh - a swampy waterlogged area, either fresh or saline.
Matrix - a medium in which something is embedded.
Mature - applied to cells and tissues that have differentiated into their final adult form assuming the function or form characteristic of cells or tissues found in a fully developed part of the plant.
Mayahuel - Aztec Goddess of Maguey ( Agave ), fertility, alcohol and pulque. Drawing of Mayahuel
Median - in the middle or axial plane.
Medulla - soft internal tissues such as pith.
Megasporangium - Pl. Megasporangia - a structure in spore-bearing plants such as Cycads in which female megaspores are formed, similar to the ovule in seed plants.
Meiacantha - with smaller or fewer spines.
Meiosis - a special type of cell division at the sexual stage of a life-cycle when the diploid or other normal chromosome number is halved in the production of haploid gametes.
Melanacanthus - with black spines.
Membrane - i. a thin pliable sheet of material that separates and forms the interface between two environments.
ii. a thin flexible sheet of tissue connecting, covering, lining, or separating various parts or organs.
iii. a thin (10 nm) structured bi-layer of phospholipid and protein molecules surrounding every biological cell and intracellular organelles such as chloroplasts, mitochondria and the cell nucleus. Functionally distinct proteins floating in the membranes of cells and organelles control the passage of substances into and out of the enclosed space, catalyse chemical reactions at the membrane surface and allow cell-cell recognition.
Meristem - the growing tissue comprised of stem cells capable of repeated division and differentiation into permanent structures.
Mescal - a strong alcoholic liquor, similar to Tequilla, made by distillation of a fermented preparation of the starchy core of Agave angustifolia and other species. Also a common Mexican name for certain Agaves.
Mescaline - a halucinogenic alkaloid found in Lophophora williamsii and other species of cactus traditionally used in native American Indian religous ceremonies and medicine.
Structure of Mescaline
Mesembrine - a narcotic alkaloid found in Scletium tortuosum (kanna) and other species of Aizoaceae (Mesembryanthemaceae). Mesembrine inhibits serotonin uptake thus increasing extracellular levels of serotonin and therefore increasing serotonergic neurotransmission. Mesembrine is also an inhibitor of the enzyme phosphodiesterase. Mesembrine is certainly mood-altering and may be an anti-depressant.
Structure of Mesembrine
Mesophyll - the photosynthetic layer of tissue of a green plant underneath the epidermis.
Microcarpa - with small fruits.
Micromeris - with small parts or divisions.
Micropyle - a small pore in a seed that allows water absorption. A minute opening in the wall of an ovule through which the pollen tube enters.
Microsperma - with small seeds.
Microsporangium - Pl. Microsporangia - a structure in spore-bearing plants e.g. Cycads in which the male microspores form, similar to the pollen sac in seed plants.
Midrib - the main or central rib of a leaf.
Mitosis - the normal process of cell division when the diploid or other normal chromosome number is conserved to produce two daughter cells with identical numbers of chromosomes to the parent cell.
Mitochondria - a functional organelle in the cell cytoplasm, of both plants and animals, containing highly ordered membrane-bound arrays of enzymes and proteins involved in respiration and energy metabolism. Mitochondria contain a small circular piece of DNA, which carries genes for a small number of mitochondrial proteins. Mitochondria are inherited almost exclusively from the female parent, and DNA sequences encoding mitochondrial genes are analysed to determine inter-specific relationships and the slow rates of mutation in mitochondrial DNA sequences are used as one form of "molecular clock."
Monocarpic - a plant that flowers only once in its life and then dies.
Monocotyledon - a large group of flowering plants with a single cotyledon that initially emerges from the seed. The Agavaceae and Liliaceae are monocotyledons.
Monoculture - growth of a single species in a particular area.
Monoecious - with both male and female reproductive organs on the same plant.
Monomorphic - with a single shape or form.
Monophyletic - of a group of organisms sharing and including a common ancestor, and including all the descendents of that common ancestor, therefore with similar characteristsics. Otherwise known as a clade.
See also: paraphyletic, polyphyletic.
Monotypic - a genus with a single representative species.
Monstrose - Monstrous - an abnormal uncoordinated form of vegetative growth, often with random production of differentiated structures, resulting in loss of normal growth habit.
Montane - occurring in mountains.
Mucilage - a water-soluble gelatinous slime, generally containing modified carbohydrates.
Mucro - a short sharp point on the tip of a flower or leaf. See also: drip tip.
Mucronate - ending with a triangular tip or a sharp point.
Multicellular - of an organism composed of many cells.
Multigeniculata - with many angled stems.
Mycorrhiza - a symbiotic relationship between certain fungi and the roots of plants, including orchids and many types of tree. Mycorrhiza may be ectotrophic, where the fungal hyphae invades the host roots or endotrophic where the fungal hyphae are entirely within the root cells. The fungal hyphae can help the roots to absorb essential nutrients and in some species are essential to the normal growth of the plant.