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The families of flowering plants

L. Watson and M.J. Dallwitz

Crassulaceae DC.

Including Isocarpellaceae Dulac, Sempervivaceae Juss.

Habit and leaf form. Herbs (mainly succulent), or shrubs (or ‘treelets’); non-laticiferous. Plants succulent. Perennial; with a basal aggregation of leaves, or without conspicuous aggregations of leaves. Xerophytic (mostly), or mesophytic, or hydrophytic (rarely). Leaves persistent; alternate, or opposite, or whorled; when alternate, spiral; flat (more or less), or terete; fleshy; petiolate to subsessile; non-sheathing; simple; peltate (sometimes), or not peltate. Lamina entire (usually), or dissected (e.g. sometimes in Bryophyllum, Kalanchoe); when dissected, pinnatifid; one-veined, or pinnately veined; cross-venulate, or without cross-venules. Leaves exstipulate. Lamina margins entire, or crenate, or serrate. Leaf development not ‘graminaceous’.

General anatomy. Plants with ‘crystal sand’, or without ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral (sometimes), or bifacial to centric (usually, and all leaf surfaces commonly covered with a bluish-white wax coating secreted from the epidermis). Hydathodes commonly present. Mucilaginous epidermis present, or absent. Stomata generally on all leaf surfaces; more or less anisocytic (surrounded by 3 subsidiaries). Hairs present, or absent (generally infrequent, but assorted forms occur); eglandular and glandular. Lamina without secretory cavities. The mesophyll containing crystals. The crystals druses, or solitary-prismatic. Minor leaf veins with phloem transfer cells (Cotyledon, Crassula, Sedum), or without phloem transfer cells (Crassula, Sedum).

Axial (stem, wood) anatomy. Cork cambium present; initially deep-seated (rarely), or initially superficial. Nodes unilacunar, or tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Cortical bundles present (commonly, representing leaf traces, sometimes centric), or absent. Medullary bundles present (commonly, sometimes developing later than the rest of the vascular system), or absent. Secondary thickening absent to developing from a conventional cambial ring (usually with little cambial activity), or anomalous (very rarely). Primary medullary rays wide, or mixed wide and narrow, or narrow.

The vessel end-walls simple. The vessels without vestured pits. The axial xylem with libriform fibres. ‘Included’ phloem absent.

Reproductive type, pollination. Plants hermaphrodite (usually). Floral nectaries present. Nectar secretion seemingly from the gynoecium (each carpel with a nectariferous appendage abaxially near the base, these usually in the form of scales, but large and petaloid in Monanthes). Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes, or in corymbs. The ultimate inflorescence units cymose. Inflorescences cincinni or corymbs. Flowers small to medium-sized; very regular (the formula being Kn, Cn, An+n, Gn — where n=3–30); (3–)5(–30) merous; cyclic; pentacyclic. Floral receptacle not markedly hollowed. Free hypanthium present (the flower usually weakly perigynous). Hypogynous disk seemingly absent (i.e. the nectariferous appendages being interpreted as gynoecial).

Perianth with distinct calyx and corolla; (6–)10(–60); 2 whorled; isomerous. Calyx (3–)5(–30); 1 whorled; polysepalous (usually), or gamosepalous (the sepals sometimes united almost to their tips, e.g. in Bryophyllum); regular; persistent; imbricate. Corolla (3–)5(–30); 1 whorled; polypetalous (commonly), or gamopetalous (the petals joined basally, or almost to the tip in Bryophyllum, Cotyledon, Kalanchöe). Corolla lobes markedly longer than the tube. Corolla imbricate; regular; white, or yellow, or pink, or purple.

Androecium (3–)5(–30). Androecial members free of the perianth, or adnate (to the corolla tube/hypanthium); free of one another (usually), or coherent (basally); when connate, 1 adelphous; 2 whorled (usually), or 1 whorled. Androecium exclusively of fertile stamens (usually), or including staminodes (e.g. some Sempervivum species). Stamens (3–)5(–30); diplostemonous (usually), or isomerous with the perianth (occasionally); alternisepalous (when 2 whorled), or oppositisepalous (when one whorled); both alternating with and opposite the corolla members. Anthers more or less basifixed; non-versatile; dehiscing via longitudinal slits; latrorse (to slightly introrse), or introrse (Crassula); bilocular; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; usually 3 aperturate; usually colporate; 2-celled.

Gynoecium (3–)5(–30) carpelled. Carpels isomerous with the perianth. Gynoecium apocarpous; eu-apocarpous to semicarpous (the carpels often slightly united at the base); superior. Carpel apically stigmatic (the style short or long); (1–)5–50 ovuled (usually ‘many’). Placentation (sub) marginal. Stigmas wet type; papillate; Group III type. Ovules pendulous to horizontal; biseriate; non-arillate; anatropous; bitegmic; crassinucellate. Outer integument sometimes contributing to the micropyle. Embryo-sac development Polygonum-type, or Allium-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral (small). Synergids pear-shaped. Endosperm formation cellular. Endosperm haustoria present; chalazal. Embryogeny caryophyllad.

Fruit non-fleshy; an aggregate. The fruiting carpels not coalescing (usually), or coalescing into a secondary syncarp (this a capsule, in Diamorpha). The fruiting carpel dehiscent; a follicle. Seeds endospermic. Endosperm oily. Cotyledons 2. Embryo achlorophyllous (2/4); straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. CAM. CAM recorded directly in Adromischus, Aeonium, Bryophyllum, Cotyledon, Crassula (including species with ‘aquatic CAM’), Cremnophila, Diamorpha, Dudleya, Echeveria, Graptopetalum, Greenovia, Hasseanthus, Hylotelephium, Kalanchoe, Lenophyllum, Monanthes, Nanathus, Pachyphytum, Parvisedum, Rochea, Sedum, Sempervivum, Tylecodon, Umbilicus, Villadia. Cyanogenic, or not cyanogenic. Alkaloids present (often), or absent. Iridoids not detected. Saponins/sapogenins present, or absent. Proanthocyanidins present, or absent; when present, cyanidin, or delphinidin, or cyanidin and delphinidin. Flavonols present, or absent; when present, kaempferol, or kaempferol and quercetin, or kaempferol, quercetin, and myricetin. Ellagic acid absent (5 species, 3 genera). Aluminium accumulation not found.

Geography, cytology. Frigid zone to tropical. Very widespread, but mainly in warm dry regions - especially in Southern Africa.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Saxifragales. Cronquist’s Subclass Rosidae; Rosales. APG III core angiosperms; core eudicot; unplaced at Superordinal level. APG IV Order Saxifragales.

Species 1500. Genera about 40; Adromisschus, Aeonium, Aichryson, Bryophyllum, Chiastophyllum, Cotyledon, Crassula, Cremnophila, Diamorpha, Dudleia, Echeveria, Graptopetalum, Greenovia, Hylotelephium, Hypagophytum, Jovibarba, Kalanchoë, Lenophyllum, Meterostachys, Monanthes, Mucizonia, Orostachys, Pachyphytum, Pagella, Parvisedum, Perrierosedum, Pistorinia, Pseudosedum, Rhodiola, Rochea, Rosularia, Sedum, Sempervivum, Sinocrassula, Telmissa, Thompsonella, Tylecodon, Umbilicus, Villadia.


There from his rocky pulpit, I heard cry
The stonecrop: See how loose to earth I grow,
And draw my juicy nurture from the sky
(Rev. R.W. Evans, quoted by Ann Pratt, ‘Wild Flowers’ (1857)

Illustrations. • Le Maout and Decaisne: Sedum, Crassula. • Kalanchoe laciniata: Thonner. • Aeonium spathulatum: as A. cruentum, Bot. Reg. 61, 1841. • Crassula capitella: as C. turrita, Bot. Reg. 1344, 1830. • Crassula decumbens, as Tillaea macrantha: Hook. Ic. Pl. 4 (1841). • Crassula tillaea: as Tillaea muscosa, Eng. Bot. 524 (1865). • Echeveria lurida Lindl., = ?: Bot. Reg. 1, 1841. • Echeveria secunda: Bot. Reg. xxvi, 57 (1840). • Kalanchöe daigremontiana (photo by Herve Brule). • Sedum, Crassula, Umbilicus: B. Ent. compilation, 1824–35. • Sedum acre: Eng. Bot. 532 (1865). • Sedum anglicum: Eng. Bot. 531 (1865). • Sedum rosea: as S. rhodiola, Eng. Bot. 525 (1865). • Sedum sexangulare: Eng. Bot. 533 (1865). • Sedum telephium ssp. purpurascens: Eng. Bot. 526 (1865). • Sempervivum arachnoideum: Bot. Mag. 2 (1788). • Sempervivum tectorum: Eng. Bot. 538 (1865). • Umbilicus rupestris: as Cotyledon umbelicus, Eng. Bot. 539 (1865).

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.’.