The families of flowering plants.
Habit and leaf form. Small trees, or shrubs (with aromatic bark); bearing essential oils. Leaves opposite; leathery; petiolate; gland-dotted; aromatic, or without marked odour; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire. Leaves without a persistent basal meristem.
Leaf anatomy. Stomata present; mainly confined to one surface; paracytic. Hairs present, or absent; when present, unicellular.
Lamina dorsiventral. The mesophyll with spherical etherial oil cells; containing calcium oxalate crystals, or without calcium oxalate crystals. The mesophyll crystals when present, solitary-prismatic. Minor leaf veins without phloem transfer cells (Calycanthus).
Stem anatomy. Cork cambium present; initially superficial. Nodes unilacunar (with two traces, or 5 or more according to Lammers et al. 1986). Cortical bundles present (the young stem with four inverted vascular bundles in the pericycle or cortex). Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids; with libriform fibres; with vessels. Vessel end-walls oblique; simple. Primary medullary rays mixed wide and narrow. Wood parenchyma paratracheal (scanty). Sieve-tube plastids P-type; type I (a).
Reproductive type, pollination. Plants hermaphrodite. Pollination entomophilous; via diptera.
Inflorescence, floral, fruit and seed morphology. Flowers solitary; terminal (on specialized, leafy short-shoots); medium-sized to large; regular; acyclic. The perianth acyclic, the androecium acyclic, and the gynoecium acyclic (the flower spiral throughout). Floral receptacle markedly hollowed. Free hypanthium present (receptacular, the flower markedly perigynous).
Perianthsequentially intergrading from sepals to petals; 15–30 (each with 3–4 vascular traces); free.
Androecium 15–55. Androecial members maturing centripetally; free of the perianth; free of one another; spirally arranged on at the top of the hypanthium. Androecium including staminodes. Staminodes 10–25; internal to the fertile stamens; non-petaloid (usually nectariferous). Stamens 5–30; laminar, or filantherous. Anthers adnate; dehiscing via longitudinal slits; extrorse (the thecae abaxial); tetrasporangiate; appendaged (by extension of the connective). The anther appendages apical. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Pollen shed as single grains. Pollen grains aperturate; 2(–3) aperturate; sulculate; 2-celled.
Gynoecium5–45 carpelled; apocarpous; eu-apocarpous (the members spirally arranged within the hypanthium); superior. Carpel stylate; apically stigmatic (the terminal style long and filiform, with a decurrent stigma); 2 ovuled (the upper one obortive). Placentation marginal. Stigmas dry type; non-papillate; Group II type. Ovules (the lower, developing one) ascending; apotropous; with ventral raphe; anatropous; bitegmic; crassinucellate, or pseudocrassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei not fusing. Antipodal cells formed; 2; not proliferating. Endosperm formation cellular.
Fruit non-fleshy (but enclosed in the fleshy hypanthium); an aggregate. The fruiting carpel indehiscent; an achene. Fruit enclosed in the fleshy hypanthium. Dispersal unit the flower. Seeds non-endospermic. Embryo well differentiated (large). Cotyledons 2; spirally twisted. Embryo achlorophyllous (1/1).
Physiology, biochemistry. Cyanogenic. Cynogenic constituents tyrosine-derived. Alkaloids present (4 species). Iridoids not detected. Proanthocyanidins absent. Flavonols present; kaempferol and quercetin, or quercetin. Ellagic acid absent (2 genera, 2 species). Arbutin absent. Saponins/sapogenins absent. Aluminium accumulation not found.
Geography, cytology. Holarctic. Temperate to sub-tropical. Eastern Asia, North America. X = 11, 12.
Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Magnoliiflorae; Laurales. Cronquist’s Subclass Magnoliidae; Laurales. APG 3 core angiosperms; Superorder Magnolianae; Order Laurales.
Species 6. Genera 3; only genera, Calycanthus, Chimonanthus, Sinocalycanthus.
Economic uses, etc. Some cultivated ornamentals, with fragrant flowers.
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