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The families of flowering plants

L. Watson and M.J. Dallwitz

Cannabidaceae Endl.

Alternatively Cannabaceae auctt., Cannabiaceae auctt., Cannabinaceae auctt.

Including Lupulaceae Link, Strobiliaceae Dulac; excluding Ulmaceae p.p.

Habit and leaf form. Herbs, or lianas; laticiferous, or with coloured juice, or non-laticiferous; resinous, or not resinous. Annual, or perennial. Self supporting (Cannabis), or climbing (Humulus); when climbing, stem twiners; Humulus twining clockwise. Mesophytic. Leaves alternate, or opposite; petiolate; non-sheathing; not gland-dotted; aromatic; simple, or compound; when compound, palmate. Lamina when simple, dissected, or entire; when lobed, palmatifid; palmately veined; cross-venulate. Leaves stipulate. Stipules intrapetiolar; free of one another; persistent. Leaf development not ‘graminaceous’.

General anatomy. Plants with laticifers, or without laticifers (always with unsegmented, unbranched coenocytes, the contents resinous in Cannabis, colourless in Humulus). The laticifers in leaves, in stems, and in the fruits.

Leaf anatomy. The leaf lamina dorsiventral. Stomata anomocytic. Hairs present (and conspicuous, see illustration); eglandular and glandular (the eglandular hairs often silicified, usually unicellular, sometimes 2-armed, less often uniseriate; the glandular ones variously capitate with unicellular, uniseriate or partiallyt biseriate stalks, discoid with unicellular stalks, or sunken with crateriform heads). Lamina with secretory cavities, or without secretory cavities. Secretory cavities in the phloem Cannabis, containing resin. Cystoliths of various sizes very commonly present (often associated with hair bases). Minor leaf veins without phloem transfer cells (Humulus).

Axial (stem, wood) anatomy. Secretory cavities present (in both genera); with resin, or with latex. Cork cambium present; initially superficial. Primary vascular tissues in a cylinder, without separate bundles to comprising a ring of bundles (the primary xylem groups in Humulus being more readily distinguished from the later formed, continuous cylinder than in Cannabis); collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring.

The vessel end-walls horizontal (or no more than slightly oblique); simple. The vessels without vestured pits. The axial xylem with libriform fibres.

Reproductive type, pollination. Fertile flowers functionally male, or functionally female, or functionally male and functionally female. Plants dioecious, or monoecious (rarely). Gynoecium of male flowers absent. Pollination anemophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’. The ultimate inflorescence units cymose. Inflorescences generally condensed-spicate. Flowers bracteate; bracteolate; regular; 5 merous; cyclic.

Perianth sepaline; 5; free (male), or joined (female); 1 whorled. Calyx 5; polysepalous (male), or partially gamosepalous (female); regular; persistent; imbricate.

Androecium 5 (in male flowers). Androecial members free of the perianth; all equal; free of one another. Androecium exclusively of fertile stamens. Stamens 5; oppositisepalous; erect in bud. Anthers dorsifixed; dehiscing via longitudinal slits; tetrasporangiate. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; 3 aperturate (usually), or 2 aperturate, or 4 aperturate, or 6 aperturate; porate; 2-celled.

Gynoecium 2 carpelled. The pistil 1 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary 1 locular. Gynoecium non-stylate, or stylate (the style very short). Styles 1; apical. Stigmas 2 (long); dry type; papillate; Group II type. Placentation apical. Ovules in the single cavity 1; pendulous; non-arillate; anatropous; bitegmic; crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids shortly pear-shaped. Endosperm formation nuclear. Embryogeny onagrad.

Fruit non-fleshy; indehiscent; a nut. Seeds endospermic. Endosperm oily. Seeds with starch. Cotyledons 2. Embryo curved (Cannabis), or coiled (Humulus). The radicle dorsal.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. C3. C3 physiology recorded directly in Cannabis. Not cyanogenic. Alkaloids present. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins present (Humulus), or absent (Cannabis); cyanidin and delphinidin (Humulus). Flavonols present; kaempferol, or kaempferol, quercetin, and myricetin. Ellagic acid absent (both genera). Sieve-tube plastids S-type (with starch).

Geography, cytology. Temperate. North temperate. X = 8, 10.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Urticales. Cronquist’s Subclass Hamamelidae; Urticales. APG III core angiosperms; core eudicot; Superorder Rosanae; fabid. APG IV Order Rosales.

Species 3. Genera 8; Aphananthe, Cannabis, Gironniera, Humulus, Lozanella, Pteroceltis, Trema.

General remarks. This compilation has not yet (2017) been updated re more recently revised family circumscriptions, involving transference of Celtis, Pteroceltis, Trema, Gironniera and Lozanella from Ulmaceae to Cannab(id)aceae; cf. Sytsma et al. (2002).


‘Grass’ is not Grass

Hops and turkies, carps and beer,
Came into England all in a year.
(Quoted by Isaac Walton in ‘The Complete Angler’, 1653)

Illustrations. • Le Maout and Decaisne: Cannabis, Humulus. • Cannabis sativa: Eng. Bot. 1280, 1868. • Humulus lupulus: Eng. Bot. 1284, 1868. • Humulus lupulus: B. Ent., 1834. • Aphananthe philippinensis: Hook. Ic. Pl. 12 (1876). • Humulus and Cannabis: leaf hairs, and leaf TS of C. sativa (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: 5th March 2018.’.