Stylochaeton Lepr.

CATE Araceae, 17 Dec 2011. araceae.e-monocot.org

Distribution

Trop. & S. Africa.

Diagnostic

Seasonally dormant or evergreen, rhizomatous geophytes; cataphylls often conspicuously mottled; leaf blade linear to cordate, sagittate or hastate, fine venation reticulate; inflorescence appearing before or with the leaves, borne at or partially below ground level; flowers unisexual, perigoniate, perigone a single cup-like structure, more conspicuous in female flowers; male flower usually with central pistillode, filaments slender, free. Differs from Zamioculcas and Gonatopus in having entire (not compound) leaves, tepals connate into a cup and spathe tube margins connate.

Habitat

Tropical humid forests (evergreen species, e.g. S. zenkeri), tropical savannas and deciduous forests (seasonally dormant species, e.g. S. natalensis); geophytes.

General Description

Laticifers absent. HABIT : seasonally dormant or evergreen herbs, rhizome subterranean, horizontal to erect, sometimes stoloniferous, roots thick, spindle-shaped, often very fleshy, almost tuberous. LEAVES : 1 to several, cataphylls often conspicuously mottled and apically auriculate, sometimes persistent as fibrous mass. PETIOLE : sheath short to long, often purplish-spotted or banded. BLADE : lanceolate, ovate, ± rounded, cordate-sagittate, sagittate, hastate-sagittate or hastate; primary lateral veins pinnate or mostly arising basally, long-arcuate and running into marginal vein, lowermost primaries sometimes retrorse and then ascending, higher order venation reticulate. INFLORESCENCE : 1-4 in each floral sympodium, appearing before or with leaves, borne at or partially below ground level. PEDUNCLE : short, much shorter than petiole. SPATHE : erect, marcescent, tube : margins connate, often ventricose at extreme base, sometimes constricted between a lower and an upper inflated zone, rarely entire spathe narrowly cylindric, blade : lanceolate-elliptic, ± gaping or opening only by narrow longitudinal slit, often much thickened. SPADIX : free, shorter than spathe, female zone densely flowered, sometimes contiguous with male zone, often separated by axis bearing a few (to many) sterile or bisexual flowers, male zone fertile to apex. FLOWERS : unisexual, perigoniate, borne in single basal whorl or in spirals; perigone a single cup-like (urceolate) structure. MALE FLOWER : perigone often with very thick, fleshy margins, stamens 2-7, free, filaments filiform, long, rarely much thickened apically, connective slender, sometimes slightly thickened, thecae oblong, dehiscing by longitudinal slit, pistillode central, cylindric to conoid, sometimes absent. POLLEN : inaperturate, or sometimes vestigially monosulcate, ellipsoid, large (mean 53 µm., range 43-58 µm.), exine foveolate-reticulate or subreticulate. FEMALE FLOWER : perigone usually greatly thickened and sticky-glandular or farinaceous on upper surface, ovary 1-4-locular, ovules 1-many per locule, anatropous, placenta basal, parietal or axile, style thick, ± cylindric, exserted beyond perigone, stigma capitate to broadly discoid and massive. BERRY : borne at or below ground level in globose to cylindric infructescence, often rugose, fleshy, 1-few-seeded. SEED : ovoid to ellipsoid, slightly compressed, testa black, thin, costate, embryo axile, elongate, endosperm copious.

J. R. Timberlake, E. S. Martins (2012). Flora Zambesiaca, Vol 12 (part 1) Araceae. Royal Botanic Gardens, Kew

Morphology General Habit

Seasonally dormant herbs (evergreen in West Africa), stem an underground rhizome, horizontal to erect, sometimes stoloniferous, roots thick, spindle-shaped, often very fleshy

Morphology Leaves

Leaves solitary to several, cataphylls often conspicuously mottled and apically auriculate, sometimes persisting as a fibrous mass Leaf blade lanceolate to ± rounded or cordate-sagittate to hastate-sagittate, base truncate, auriculate or cordate; primary lateral veins pinnate or mostly arising basally, higher order venation reticulate

Morphology Leaves Petiole

Petiole with a long sheath, sheath usually narrowing upwards or apically obtuse, rarely auriculate

Morphology Reproductive morphology Inflorescences

Inflorescences 1–4, produced with or before leaf; peduncle short, borne at or below ground level; spathe tube with united margin in lower part, often inflated at extreme base; sometimes constricted between a lower and upper inflated zone, rarely entire spathe narrowly cylindric or conic; spathe blade lanceolate-elliptic, ± gaping or unexpanded with a longitudinal slit, often greatly thickened

Morphology Reproductive morphology Inflorescences Spadix

Spadix usually sessile, rarely stipitate, shorter than spathe; female zone densely flowered, contiguous with male zone, or separated by an axis naked or bearing sterile or bisexual flowers; male zone fertile to apex

Morphology Reproductive morphology Flowers

Male flowers often with thick fleshy margins of perigone, stamens 2–7; filaments filiform, long, rarely thickened apically, connective slender, sometimes slightly thickened, anther dehiscing by longitudinal slits, central pistillode usually present Female flowers in single whorl or in spirals; perigone usually greatly thickened, glandular or mealy on upper surface; ovary 1–4-locular, ovules 1 to many per locule, anatropous, placenta basal, parietal or axile; stylar region thick, ± cylindric, exserted beyond perigone; stigma capitate to broadly discoid and massive Flowers unisexual, surrounded by a single cup-like perigone

Morphology Reproductive morphology Fruits

Fruit a berry, borne at or below ground level in a globose to cylindric infructescence, often rugose, 1 to few seeded

Morphology Reproductive morphology Seeds

Seeds ovoid to ellipsoid; testa thin, black 2n = 28 or 56.

Distribution

A genus of c.19 species endemic to tropical and SE subtropical Africa, with its centre of diversity in Tanzania; 6 species in the Flora area.

M. Thulin et al. Flora of Somalia, Vol. 1-4 [updated 2008] https://plants.jstor.org/collection/FLOS

Morphology General Habit

Herbs with underground rhizome and fleshy roots

Morphology Leaves

Leaves basal, solitary to several; blade lanceolate, ovate, cordate-sagittate, sagittate or hastate-sagittate

Morphology Reproductive morphology Inflorescences

Inflorescences borne at or below ground-level on short peduncles, produced before or with the leaves Spadix monoecious with pistillate part near the base and long staminate part above, often with a zone of sterile flowers between

Morphology Reproductive morphology Inflorescences Bracts Spathe

Spathe forming a tube in lower part, upper part a lanceolate-elliptic ± expanded limb, or unexpanded with a lateral slit

Morphology Reproductive morphology Flowers

Female flowers with 1–2-celled ovary; stigma capitate to broadly disc-shaped Male flowers with 2–7 stamens; filaments subulate; anthers dehiscing by lateral slits Flowers unisexual, surrounded by ± glandular cup-shaped perianth

Morphology Reproductive morphology Fruits

Berries borne at or below ground-level in globose to cylindric infructescence, 1–few-seeded

Morphology Reproductive morphology Seeds

Seeds with endosperm.

Distribution

Some 20 species in tropical and southern subtropical Africa.

Note

The inflorescences are very inconspicuous, often developing partly below ground and appearing before the leaves. The present account is provisional and more detailed field work is needed.