Genera of the Plants of the United States: Malvastrum

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Malvastrum, Gray.

Involucellum nullum vel 1–3-phyllum. Stigmata terminalia, capitellata. Ovulum in loculis solitarium, peritropo-adscendens. Fructus 5–20-coccus, carpellis muticis rostratisve ab axi secenditibus. Semen reniforme. Embryo arcuatus vel annularis; radicula centripeto-infera.

MALVASTRUM, Gray, Pl. Fendl. in Mem. Amer. Acad. (n. ser. 4.) p. 21.
MALVÆ et SIDÆ Sp., Auct.

CALYX naked or furnished with an involucel or from one to three subulate and deciduous bractlets, or sometimes with a conspicuous three-leaved persistent involucel, five-cleft, persistent; the segments valvate in æstivation. PETALS 5, hypogynous, usually oblique or obliquely emarginate, convolute in æstivation. STAMENS indefinite, monadelphous in a simple column, the base of which is united with the claws of the petals, hypogynous: FILAMENTS all arising from the summit of the column: ANTHERS reniform, one-celled, opening around the whole convex side. OVARIES 5 to 20, united in a circle around a central receptacle: STYLES as many as the ovaries, united below; STIGMAS terminal, capitate. OVULE solitary in each carpel, peritropous-ascending; amphitropous, the micropyle inferior.

FRUIT a ring of coriaceous or crustaceous reniform one-seeded carpels, which at length separate from each other and from the central axis, and open by rupture on the inner edge, or are indehiscent, or sometimes two-valved, pointless or rostrate, and sometimes bearing two tubercules or short spines on the back. SEED reniform: EMBRYO curved into a semicircle around a little soft albumen, or incompletely annualar: COTYLEDONS broad and foliaceous, cordate, conduplicate-infolded: RADICLE centripetal-inferior.

HERBS or low shrubby plants, with alternate stipulate leaves, and axillary or racemose, spicate or glomerate flowers. Corolla flame-colored, orange-colored, or yellow.

ETYMOLOGY. Name prolonged from Malva; given by De Candolle to his section of that genus which included the true Mallows as well as many which are referrible to the presesnt genus, as constituted in Plantæ Fendlerianæ, l. c.

GEOGRAPHICAL DISTRIBUTION &c. The genus comprises a considerable number of species, chiefly American, and indigenous to the warmer parts of the country, from the plains of Missouri to those of Paraguay and the Andes of Chili [1]. It probably should also comprise the Malvæ § Capenses [2] of De Candolle; but it has no European representatives.

NOTE: The species have been variously referred, those with a small or caducous involucel, or none at all, to Sida, from which they differ in their ascending ovule and inferior radicle; those with manifest involucel usually to Malva, from which their capitate stigmas at once distinguish them.

[1] The genus has subsequently been further divided: Fuertesimalva, for example, is a segregate therefrom. This may narrow the diagnosis of the genus given above.
[2] Malva § Capenses may correspond to Anisodontea, which is a South African genus allied to Malvastrum.

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