Thelymitra J.R.Forst. & G.Forst.
Sun Orchids

Scientific Description

Family Orchidaceae.

Habit and leaf form. Herbs. Plants succulent (leaves of many species fleshy), or non-succulent. Perennial. Leaves basal (sheathing at the base). Tuberous (tubers ovoid). Helophytic, or mesophytic, or xerophytic. Leaves medium-sized to large; ‘herbaceous’, or leathery, or fleshy; petiolate; simple. Leaf blades entire; flat, or rolled (channelled), or solid; when ‘solid’, terete; parallel-veined; cross-venulate, or without cross-venules. Leaf blade margins entire. Vernation conduplicate. Leaf anatomy. Hairs absent (usually), or present (T. villosa). Stem anatomy. Secondary thickening absent.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous, or pollinated by unusual means (self-pollinated). Pollination mechanism conspicuously specialized.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’. Inflorescence few-flowered to many-flowered. Flowers when aggregated, in racemes. The terminal inflorescence unit racemose. Inflorescences scapiflorous, or not scapiflorous; terminal; stem bracts 1–3. Flowers pedicellate (pedicels usually long); small to large (decreasing in size up the raceme, usually opening only in strong sunshine); fragrant, or odourless; somewhat irregular to very irregular; zygomorphic; resupinate. The floral asymmetry involving the androecium. Flowers 3 merous; cyclic; supposedly basically pentacyclic. Perigone tube absent. Perianth of ‘tepals’, or with distinct calyx and corolla, or petaline (by misinterpretation); 6; 2 -whorled, or 1 -whorled (by misinterpretation); isomerous; free; petaloid; without spots, or spotted; colourful, cream, or yellow, or orange, or red to pink, or purple, or blue, or brown. Calyx (if the outer whorl be so designated) 3 (the median member ostensibly posterior); 1 -whorled; polysepalous. Corolla (i.e. the members of the inner whorl) 3, or 6 (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 erect); coherent (via the gynostemium); 1 - adelphous; theoretically 2 -whorled. Androecium including staminodes, or exclusively of fertile stamens (by misinterpretation). Staminodes 2 (represented in most species by 2 prominent arms flanking the anther, frequently adorned with glands, calli or tufts of hair). 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 either mealy in self-pollinating species, or aggregated into a pollinarium in insect-pollinated species). 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; 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, South Australia, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania.

Additional characters Perianth without labellum (the sepals and petals all similar, the inner perianth member scarcely distinguishable from the other segments). Leaves solitary. Leaves erect. Column prominently winged (wings shortly connate in front at the base, produced on each side of the anther into a lateral lobe and often extended behind and over the anther to form a hood; lateral lobes often toothed or terminating in a tuft of hairs), or not prominently winged. Perianth not glossy.