The families of flowering plants
Habit and leaf form. Lianas to herbs (large and robust to small and herbaceous, parasitic twiners); bearing essential oils (the crushed shoots being faintly aromatic). Switch-plants; with the principal photosynthesizing function transferred to stems. Leaves much reduced. Plants partially parasitic (dodderlike). Parasitic on aerial parts of the host (with haustoria). Perennial. Climbing; stem twiners. Mesophytic. Leaves minute to small; alternate; spiral; membranous; non-sheathing; gland-dotted, or not gland-dotted (?); simple; peltate, or not peltate; exstipulate.
Leaf anatomy. The mesophyll with spherical etherial oil cells, or without etherial oil cells (?); containing mucilage cells, or not containing mucilage cells (?).
Axial (stem, wood) anatomy. Cork cambium absent (?). Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles (with strands of phloem situated in furrows on the oter periphery of the xylem). Internal phloem absent. Secondary thickening developing from a conventional cambial ring (?).
The vessel end-walls simple. Included phloem absent.
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in inflorescences; in racemes, or in spikes, or in heads, or in umbels, or in panicles. Inflorescences axillary; sessile or pedunculate heads, panicles, spikes, umbels and racemes; without involucral bracts. Flowers minute to small; regular; 3 merous; cyclic; polycyclic. Free hypanthium present (this at first short, but later accrescent).
Perianth with distinct calyx and corolla; 6; 2 whorled; isomerous. Calyx 3; 1 whorled; non-fleshy (scale-like); persistent; non-accrescent. Corolla 3; 1 whorled; polypetalous; regular; white, or yellow; fleshy; non-accrescent. Petals sessile.
Androecium 12. Androecial members free of the perianth, or free of the perianth and adnate (with outer staminodes adnate to the corolla); free of one another; 4 whorled (whorls of 3). Androecium including staminodes. Staminodes 3–6; internal to the fertile stamens (in 12 whorls). Stamens (6–)9; diplostemonous to triplostemonous; somewhat laminar to petaloid (by expansion of the filament and connective), or filantherous. Anthers basifixed; non-versatile; dehiscing by longitudinal valves (cf Lauraceae, opening from the base upwards?); extrorse; bilocular; bisporangiate, or tetrasporangiate, or bisporangiate and tetrasporangiate (?). Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis successive. Anther wall initially with more than one middle layer; of the basic type. Tapetum glandular. Pollen grains nonaperturate; 2-celled.
Gynoecium 1 carpelled (ostensibly), or 3 carpelled (theoretically). The pistil 1 celled. Gynoecium ostensibly monomerous; of one carpel (or at least, ostensibly so); superior. Carpel stylate; apically stigmatic; 1 ovuled. Placentation apical. Ovules pendulous; apotropous; with dorsal raphe; non-arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Endothelium not differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed, or not formed; not proliferating. Hypostase absent. Endosperm formation cellular. Endosperm haustoria absent.
Fruit fleshy. The fruiting carpel indehiscent; baccate. Fruit enclosed in the fleshy hypanthium; 1 seeded. Seeds non-endospermic. Embryo well differentiated. Embryo achlorophyllous; straight.
Physiology, phytochemistry. Not cyanogenic. Arbutin absent. Iridoids not detected. Saponins/sapogenins absent. Ellagic acid absent.
Geography, cytology. Paleotropical, Australian, and Antarctic. Temperate to tropical. Africa, Indonesia, New Guinea, Australia, New Zealand. Supposed basic chromosome number of family: 12.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgrens Superorder Magnoliiflorae; Laurales. Cronquists Subclass Magnoliidae; Laurales. APG 3 Order Laurales (as a synonym of Lauraceae).
Species 17. Genera 1; only genus, Cassytha.
General remarks. Usually treated as an inconveniently aberrant subfamily of Lauraceae, which seems unnecessary even under cladistic dogma. In addition to comprising partially parasitic, twining switch plants having stems without secondary thickening or cork and with reduced, membranous leaves, Cassytha differs in conspicuous perianth details, ovules with the outer integument contributing to the micropyle, and and perhaps in the absence of inulin.
Illustrations. • Technical details: Cassytha. • Technical details: Cassytha (Lindley). • Cassytha racemosa: flowers (photos). • Cassytha racemosa: habit (photo).
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: 20th July 2017. delta-intkey.com/angio’.