Pothoidium Schott

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

General Description

HABIT : climbing herb, stems somewhat woody, flowering branches free and hanging. LEAVES : distichous, many. PETIOLE : oblong, entirely flattened, resembling blade, venation parallel, joined to blade by constricted articulation. BLADE : much shorter than petiole, triangular-lanceolate; midrib absent, no primary veins differentiated, veins parallel, running into apex. INFLORESCENCE : several to many, borne in a terminal branching system, lower inflorescences axillary to a foliage leaf, upper ones either subtended by cataphyll-like leaf or without subtending leaf. PEDUNCLE : peduncular axis slender, composed of one to several internodes, sometimes subtended by a prophyll, sometimes also bearing a cataphyll ± halfway up. SPATHE : occurrence irregular, often absent, linear-lanceolate, widely spreading, margins usually revolute. SPADIX : apparently often functionally unisexual, cylindric, sessile to long-stipitate when subtended by spathe. FLOWERS : apparently usually unisexual, sometimes bisexual, perigoniate, male flowers with well developed anthers and apparently sterile ovary, female flowers with large fertile ovary and lacking stamens; tepals 6, fornicate, membranaceous. STAMENS : 3-6, number often varying on single spadix, filaments elongated and overtopping perigone at anthesis, oblong-triangular, flattened, connective slender, thecae short, ellipsoid, dehiscing by broad slit. POLLEN : monosulcate, ellipsoid-oblong, medium-sized (mean 26 µm.), exine reticulate with psilate muri, apertural exine shallowly fossulate or verrucate. GYNOECIUM : broadly ovoid to subglobose or obovoid, ovary 1-locular, ovule 1, anatropous, funicle short, placenta subbasal, stylar region attenuate, stigma discoid-hemispheric. BERRY : ellipsoid to ovoid, apiculate (stigma remnant), prominently exserted when mature, red. SEED : ellipsoid, testa smooth, embryo large, endosperm absent.

Habitat

Tropical humid forest; climbing hemiepiphyte.

Diagnostic

Evergreen, climbing hemiepiphytes; leaves distichous; petiole entirely flattened, resembling blade; leaf blade much shorter than petiole, midrib absent, fine venation parallel; inflorescences several, in terminal branching system, spathe often absent; flowers apparently usually unisexual, sometimes bisexual, perigoniate with 6 free tepals. Differs from Pothos in having 1-locular ovaries and flowering shoots terminating in a branching system of spadices and often functionally unisexual. Pothoidium is similar to Pothos repens but differs in being functionally dioecious, by the branching inflorescences, and by its unilocular ovary and solitary ovule. Pothoidium has functionally unisexual spadices arranged seemingly in panicles and maturing sequentially. The structure of the fertile shoots is not yet clearly understood; however, it is possible that they are developed by the reduction of all the leaves of a leafy fertile shoot system to minute prophylls and cataphylls and that the panicle-like synflorescence is hence to be regarded as an aggregate structure. Pothos repens and Pothoidium are vegetatively almost identical. Depauperate flowering specimens of Pothoidium greatly resemble robust plants of Pothos repens. Interpretation of Pothoidium inflorescences suggests that P. lobbianum is functionally dioecious. “Male” spadices have flowers with prominently visible anthers and an apparently sterile ovary. “Female” spadices have flowers with a large unilocular fertile ovary and no stamens. Flowers of Pothos species are always bisexual with a 3-locular ovary.

Distribution

Taiwan, Malesia.