Nervilia Gaudich.
Shield Orchids

Scientific Description

Family Orchidaceae.

Habit and leaf form. Herbs (usually colony-forming); deciduous. Leaves well developed (the leaf appearing after flowering on a separate stalk, lasting for several months), or absent (by misinterpretation). Plants succulent, or non-succulent. Perennial. Leaves basal. Tuberous (tubers globular). Helophytic, or mesophytic. Leaves medium-sized to large; ‘herbaceous’, or leathery, or fleshy; petiolate; simple. Leaf blades entire; flat; ovate; parallel-veined; cross-venulate, or without cross-venules; cordate. Leaf blade margins entire. Vernation plicate. Stem anatomy. Secondary thickening absent.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous. Pollination mechanism conspicuously specialized.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’. Inflorescence few-flowered. Flowers in racemes. The terminal inflorescence unit racemose. Inflorescences scapiflorous, or not scapiflorous; terminal; erect, the flowering stem elongating after fertilization. Flowers pedicellate; small to large; fragrant; very irregular; zygomorphic; resupinate. The floral asymmetry involving the perianth and involving the androecium. Flowers 3 merous; cyclic; supposedly basically pentacyclic. Perigone tube absent. Perianth of ‘tepals’, or with distinct calyx and corolla; 6; 2 -whorled; isomerous (but zygomorphic); free; sepaloid and petaloid; green, or cream, or pink, or purple. Calyx (if the outer whorl be so designated) 3 (the median member ostensibly posterior), or 5 (by misinterpretation); 1 -whorled; polysepalous. Corolla (i.e. the members of the inner whorl) 3, or 1 (by misinterpretation); polypetalous; imbricate. Androecium 3, or 1 (by misinterpretation). Androecial members free of the perianth; united with the gynoecium (fused with the style to form a column or ‘gynostemium’; column long, dilated at apex); coherent (via the gynostemium); 1 - adelphous; theoretically 2 -whorled. Androecium including staminodes, or exclusively of fertile stamens (by misinterpretation). Staminodes 2 (these anterior (ostensibly posterior), supposedly the abaxial pair of the inner whorl). Stamens 1 (this across the flower from the labellum, i.e. anterior but ostensibly posterior, supposedly representing the outer whorl); reduced in number relative to the adjacent perianth; alterniperianthial (i.e. with reference to the single stamen, across the flower from the labellum); filantherous, or with sessile anthers. Anthers dorsifixed to basifixed; dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged, or unappendaged. Pollen shed in aggregates; in the form of pollinia (pollinia 2, grooved). Gynoecium 3 carpelled. The pistil 1 celled. Carpels isomerous with the perianth. Gynoecium syncarpous; eu-syncarpous; inferior. Ovary unilocular; 1 locular. The ‘odd’ carpel anterior (away from the labellum). Gynoecium stylate. Styles 1 (inflexed); apical. Stigmas 1 (in a slight recess at anterior apex of column); 3 - lobed (but becoming much modified in form, the apex of the median lobe forming the ‘rostellum’); wet type; papillate; Group III type. Placentation parietal. Ovules not differentiated; in the single cavity 30–100 (i.e. very numerous); non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules septicidal, or loculicidal. Fruit 30–500 seeded (i.e. seeds usually very numerous). Seeds endospermic (endosperm development arrested very early), or non-endospermic; minute; without starch. Embryo rudimentary at the time of seed release, or weakly differentiated. Seedling. Seedling collar not conspicuous. Primary root ephemeral.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, and Queensland. Northern Botanical Province.

Additional characters Perianth of 5 similar members and the median inner member modified into the labellum (sepals and lateral petals rather long and narrow; labellum sessile, 3-lobed or occasionally entire, coloured differently to the other perianth segments; lateral lobes erect and involute, usually encircling the column). Leaves solitary. Leaves ground-hugging, or erect. Labellum not insect-like. Labellum not motile. Perianth not glossy.