Alternatively Papayaceae Blume
Habit and leaf form. Small, soft-stemmed, palmlike trees, or shrubs, or herbs (prostrate, Jarilla only); laticiferous. Plants succulent (in the stem), or non-succulent. Pachycaul (commonly, with unbranched trunk and a terminal cluster of leaves), or leptocaul. Leaves large; alternate; petiolate; simple, or compound; commonly palmate (the leaflets sometimes pinnately lobed). Lamina when simple, entire (usually, more or less), or dissected (rarely); when simple, palmatifid (usually), or pinnatifid (rarely); palmately veined (usually), or pinnately veined (rarely, when simple and entire or pinnately lobed); cross-venulate. Leaves exstipulate (usually), or stipulate. Stipules when present, spiny.
General anatomy. Plants with laticifers (articulated, anastomosing). The laticifers in leaves and in stems.
Leaf anatomy. Stomata present; anomocytic (Carica papaya).
Lamina dorsiventral. The mesophyll containing calcium oxalate crystals. The mesophyll crystals druses. Minor leaf veins without phloem transfer cells (Carica).
Stem anatomy. Nodes tri-lacunar, or multilacunar. Cortical bundles absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones. ‘Included’ phloem absent. Vessel end-walls simple. Vessels without vestured pits.
Reproductive type, pollination. Unisexual flowers present. Plants monoecious, or dioecious, or andromonoecious, or gynomonoecious, or polygamomonoecious (? — usually dioecious or monoecious, but sometimes with some perfect flowers). Gynoecium of male flowers vestigial, or absent.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes. The ultimate inflorescence unit cymose. Inflorescences axillary; loose, axillary, cymose. Flowers regular; 5 merous; cyclic. Free hypanthium absent.
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5 (small); 1 whorled; polysepalous, or gamosepalous; blunt-lobed, or toothed; regular; open. Corolla 5; 1 whorled; gamopetalous; contorted, or valvate; with a short tube in female flowers, a long one in male flowers; regular.
Androecium in male flowers, 5, or 10. Androecial members adnate (to the corolla tube); free of one another (Carica), or coherent (basally connate); when joined, 1 adelphous (forming a short tube); 1 whorled, or 2 whorled. Androecium (male flowers) exclusively of fertile stamens. Stamens 5, or 10; inserted in the throat of the corolla tube; isomerous with the perianth, or diplostemonous; oppositisepalous; alternating with the corolla members, or both alternating with and opposite the corolla members; filantherous, or with sessile anthers. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged (via a shortly prolonged connective), or unappendaged (?). Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer. Tapetum glandular. Pollen grains aperturate; 3 aperturate; colporate; 2-celled.
Gynoecium 5 carpelled; partly petaloid (e.g. with petaloid stigmas), or non-petaloid. Carpels isomerous with the perianth. The pistil 1 celled, or 5 celled. Gynoecium syncarpous; synovarious to synstylovarious; superior. Ovary 1 locular, or 5 locular. Gynoecium stylate. Styles 1, or 5; free to partially joined; apical. Stigmas 5; dry type; papillate; Group II type. Placentation when unilocular, parietal (the placentas more or less deeply intruded), or laminar-dispersed; when plurilocular, axile. Ovules in the single cavity 50–100 (or more — ‘many’); 30–50 per locule (or more — ‘many’); funicled (the funicle more or less enlarged); anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids apically broad, with filiform apparatus. Endosperm formation nuclear. Embryogeny by irregular early cleavages.
Fruit fleshy; indehiscent; a berry (large, melonlike). Seeds endospermic. Endosperm oily. Embryo well differentiated. Cotyledons 2 (broad, flat). Embryo achlorophyllous (1/1); straight.
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Mustard-oils present (often). Not cyanogenic. Alkaloids present (carpaine), or absent. Iridoids not detected. Proanthocyanidins absent. Flavonols absent. Ellagic acid absent (Carica). Saponins/sapogenins present, or absent. C3. C3 physiology recorded directly in Carica.
Geography, cytology. Paleotropical and Neotropical. Sub-tropical and tropical. Tropical America (mainly) and West Africa (Cylicomorpha). X = 9.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Violiflorae; Violales. Cronquist’s Subclass Dilleniidae; Violales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Brassicales.
Species 55. Genera 4; Carica, Cylicomorpha, Jacaratia, Jarilla.
Economic uses, etc. Commercial edible fruit (papaw, pawpaw, papaya) from C. papaya.
• Technical details: Carica (Lindley).