Arisarum Mill.

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

General Description

HABIT : small, seasonally dormant herbs, stem an ovoid to cylindric tuber or slender rhizome ( A. proboscideum) with stolons. LEAVES : 1-2(-3). PETIOLE : often sparsely spotted, sheath short. BLADE : cordate-sagittate to subhastate; primary lateral veins pinnate and also arising at petiole insertion, forming submarginal collective vein, 2 marginal veins also present, higher order venation reticulate. INFLORESCENCE : solitary, appearing with leaves. PEDUNCLE : shorter or equalling leaf, often spotted. SPATHE : eventually evanescent, tube erect, margins connate, cylindric to subventricose, slightly constricted at apex, blade ± curved forward, fornicate, gaping, sometimes subtomentose, apex cuspidate or drawn out into a very long, erect to twisted thread, greenish or brownish or purple-brown, at base white or with white to pale green longitudinal stripes. SPADIX : female zone adnate to spathe, 2-5-flowered, contiguous with male zone, male zone laxly flowered, extending for more than half spathe tube length, terminal appendix naked, either stipitate with massive apical knob, or stipitate with thick, clavate, basally truncate, fungoid, apical region, or not stipitate and slenderly clavate. FLOWERS : unisexual, perigone absent. MALE FLOWER : 1-androus, filament terete, as long or longer than anther, anther peltately attached, horseshoe-shaped, connective slender, thecae oblong, apically confluent, dehiscing by single continuous slit. POLLEN : pollen shed in amorphous mass, inaperturate, ellipsoid- elongate, medium-sized (mean 45 µm., range 43-46 µm.), exine striate to foveo-reticulate. FEMALE FLOWER : ovary 1-locular, depressed-globose, ovules several, orthotropous, funicle short, placenta basal, style ± abruptly narrowed, stigma small, subhemispheric. BERRY : hemispheric, flattened at apex with elevated angled margins, few-seeded, pericarp carnose-leathery, style base persistent. SEED : ovoid, with large, irregularly conoid strophiole (aril), testa longitudinally rugose, embryo terete, straight, axile, endosperm copious.

Habitat

Warm temperate scrub and woodland; geophytes, on stony ground in macchie (“maquis”), between rocks or under trees and shrubs.

Distribution

Macaronesia, Medit. to W. Transcaucasus.

Diagnostic

Small, seasonally dormant geophytes; leaves few (1-3), blade cordate-sagittate, with reticulate fine venation; spathe tube with connate margins; spadix with sterile terminal appendix; flowers unisexual, perigone absent; female zone adnate to spathe. Differs from Arisaema in always having both sexes present in the same inflorescence, lower spathe margins connate and simple leaf blades.