The Families of Flowering Plants

L. Watson and M. J. Dallwitz


Crassulaceae DC.

Including Isocarpellaceae Dulac, Sempervivaceae Juss.

Habit and leaf form. Herbs, or shrubs (or ‘treelets’). Plants succulent. Perennial; with a basal aggregation of leaves, or with neither basal nor terminal aggregations of leaves. Xerophytic (mostly), or mesophytic, or hydrophytic (rarely). Leaves evergreen; alternate, or opposite, or whorled; when alternate, spiral; flat (more or less), or terete; fleshy; petiolate to subsessile; non-sheathing; not gland-dotted; 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. Leaves without a persistent basal meristem.

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

Leaf anatomy. Hydathodes commonly present. Mucilaginous epidermis present, or absent.

Lamina dorsiventral (sometimes), or isobilateral to centric (usually). Minor leaf veins with phloem transfer cells (Cotyledon, Crassula, Sedum), or without phloem transfer cells (Crassula, Sedum).

Stem anatomy. Cork cambium present; initially deep-seated (rarely), or superficial. Nodes unilacunar, or tri-lacunar. Cortical bundles present (commonly), or absent. Medullary bundles present (commonly), or absent. Internal phloem absent. Secondary thickening mostly developing from a conventional cambial ring (very occasionally ‘anomalous’). ‘Included’ phloem absent. Xylem with libriform fibres; with vessels. Vessel end-walls simple.

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). Entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, or in corymbs. The terminal inflorescence unit 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; regular; persistent; imbricate. Corolla (3–)5(–30); 1 whorled; polypetalous (usually), or gamopetalous (basally). 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, biochemistry. Cyanogenic, or not cyanogenic. Alkaloids present (often), or absent. Iridoids not detected. 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). Saponins/sapogenins present, or absent. Aluminium accumulation not found. 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.

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 (1998) Eudicot; core Eudicot; Rosid; 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.

Illustrations.1 Sempervivum arachnoideum. Sedum, Crassula, Umbilicus. Technical details (Sedum, Crassula). Technical details (Kalanchoe laciniata).

Quotations
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)

Cite this publication as: ‘L. Watson and M. J. Dallwitz (1992 onwards). The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 27th September 2000. http://biodiversity.uno.edu/delta/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), and Watson and Dallwitz (1991) should also be cited (see References2).
1 URLs for illustrations given in article 2 References
  • http://www.keil.ukans.edu/delta/angio/www/refs.htm

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