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The families of flowering plants

L. Watson and M. J. Dallwitz

Calycanthaceae Lindl.

Excluding Idiospermaceae.

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. Leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral. Stomata present; mainly confined to one surface; paracytic. Hairs present, or absent; when present, unicellular. Lamina without secretory cavities. The mesophyll with spherical etherial oil cells; containing crystals, or without crystals. The crystals when present, solitary-prismatic. Minor leaf veins without phloem transfer cells (Calycanthus).

Axial (stem, wood) anatomy. Young stems with solid internodes. Pith homogeneous (comprising thin-walled parenchyma). Secretory cavities absent. Cork cambium present; initially superficial. Nodes unilacunar (with two traces, or 5 or more according to Lammers et al. 1986). Internal phloem absent. Cortical bundles present (the young stem with four inverted vascular bundles in the pericycle or cortex). Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays mixed wide and narrow.

The wood ring porous to semi-ring porous. The vessels very small (20–25 microns); in radial multiples, clustered, and in tangential arcs. The vessel end-walls oblique; simple. The vessels with spiral thickening. The axial xylem with tracheids; commonly with vasicentric tracheids; with fibre tracheids; with libriform fibres. The parenchyma scanty paratracheal. The secondary phloem not stratified. ‘Included’ phloem absent. The wood partially storied.

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).

Perianth sequentially 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.

Gynoecium 5–45 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).

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Cyanogenic. Cynogenic constituents tyrosine-derived. Alkaloids present (4 species). Arbutin absent. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins absent. Flavonols present; kaempferol and quercetin, or quercetin. Ellagic acid absent (2 genera, 2 species). Aluminium accumulation not found. Sieve-tube plastids P-type; type I (a).

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.

Illustrations. • Technical details: Calycanthus, Chimonanthus. • Technical details: Calycanthus: (Lindley). • Calycanthus floridus: Bot. Mag. 503, 1801. • Calycanthus floridus: Bot. Mag. 503, 1801. • Calycanthus: leaf hairs and stem TS (Solereder, 1908).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 19th October 2016.’.