| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Petrosaviaceae Hutch.

~ Liliaceae, Melanthiaceae

Habit and leaf form. Herbs. More or less ‘normal’ plants to switch-plants (with slender, simple, erect stems). Leaves much reduced (colourless, bractlike). Plants autotrophic (Japonolirion), or parasitic; when parasitic, mycoheterotrophic; green and photosynthesizing, or not green. Without conspicuous aggregations of leaves. Self supporting. Leaves small; alternate; spiral; membranous; sessile; sheathing; with blades ‘normally orientated’; simple. Lamina entire.

General anatomy. Plants without laticifers.

Axial (stem, wood) anatomy. The axial xylem without vessels.

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present (septal). Nectar secretion from the gynoecium.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in corymbs. The ultimate inflorescence units racemose (?). Inflorescences terminal; "in terminal corymbiform racemes" - Hutchinson. Flowers bracteate; small; regular; 3 merous; pentacyclic. Perigone tube absent. Hypogynous disk absent.

Perianth of ‘tepals’; 6; free; 2 whorled; isomerous; sepaloid; more or less similar in the two whorls ("sub-similar"); colourless; non-fleshy; persistent.

Androecium 6. Androecial members free of the perianth to adnate (to the bases of the persistent perianth segments); more or less all equal; free of one another; ostensiby 1 whorled. Stamens 6; diplostemonous (cf. illustrations); oppositiperianthial (?); filantherous (with slender filaments). Anthers dorsifixed; dehiscing via short slits to dehiscing via longitudinal slits; ovate, introrse. Microsporogenesis simultaneous. Pollen grains aperturate; 1 aperturate; sulcate.

Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. Gynoecium more or less apocarpous (the carpels "free almost to the base"); eu-apocarpous; superior. Carpel non-stylate to stylate ("the sub-capitate stigma on a very short style"); apically stigmatic; 15–100 ovuled ("many"). Placentation marginal.

Fruit non-fleshy; an aggregate. The fruiting carpel dehiscent; a follicle (opening via an adaxial slit). Seeds numerous, ribbed. Cotyledons presumably 1.

Seedling. Primary root ephemeral (?).

Geography, cytology. Paleotropical. Sub-tropical and tropical. Malesia, Borneo, S. China, S. Japan.

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Melanthiales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Petrosaviales.

Species 3, or 4 (if Japonolirion is included). Genera 1, or 2; Petrosavia, (Japonolirion?).

General remarks. Current description mostly from Hutchinson (1964), restricted to Petrosavia. Recent assignment here by APG adherents of the taxonomically problematic, autotrophic Japanese endemic Japonolirion osense is unconvincing.

Illustrations. • Petrosavia stellaris: Hutchinson (1964).

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: 8th June 2026. delta-intkey.com’.

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