Dendrolobium (Wight & Arn.) Benth.

Scientific Description

Family Papilionaceae. Desmodieae.

Sometimes included in Desmodium.

Habit and leaf form. Ours small, sericeous shrubs (with small hooked hairs as well). Plants unarmed. To 0.3–0.6 m high. Mesophytic, or xerophytic. Leaves small to medium-sized; not fasciculate; alternate; spiral; ‘herbaceous’, or leathery; not imbricate; petiolate; non-sheathing; not gland-dotted; compound; pulvinate; unifoliolate and ternate (the illustration in Wheeler et al depicting 5-foliolate leaves being contradicted by their own and other descriptions of D. stipatum). Leaves when trifoliolate, pinnately trifoliolate. Leaflets 1, or 3. Lateral leaflets opposite. Leaflets stipellate; pulvinate, or epulvinate; flat; without lateral lobes. Leaf blades dorsiventral; cross-venulate. Leaves with stipules. Stipules intrapetiolar; free of one another; 3–7 mm long, triangular. Leaf blade margins entire; flat. Leaves without a persistent basal meristem. Stem anatomy. Nodes tri-lacunar, or penta-lacunar. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous, or ornithophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in racemes, or in umbels. Inflorescences simple. The terminal inflorescence unit racemose. Inflorescences axillary; in ours shortly pedunculate axillary racemes, reduced almost to umbels. Flowers pedicellate; bracteate. Bracts deciduous (scarious). Flowers (bi-) bracteolate (similar to the bracts, just below the calyx). Bracteoles deciduous. Flowers small (5–7 mm long in ours); very irregular; zygomorphic; resupinate, or not resupinate. The floral asymmetry involving the perianth, or involving the perianth and involving the androecium. Flowers papilionaceous (imbricate-descending, with the posterior petal outside and forming the ‘standard’); basically 5 merous. Floral receptacle with neither androphore nor gynophore. Free hypanthium present, or absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; 4–5 lobed. Calyx lobes markedly shorter than the tube, or about the same length as the tube. Calyx imbricate, or valvate; exceeded by the corolla; bilabiate (the posterior pair of members connate for all or much of their length); non-fleshy; persistent; non-accrescent; with the median member anterior (this member often somewhat longer than the laterals). Epicalyx absent. Corolla present; 5; 1 -whorled. Standard not appendaged. Corolla partially gamopetalous. 2 of the petals joined (the two ventral petals connivent to form the ‘keel’). The joined petals of the papilionate corolla anterior. The wings of the corolla free from the keel; not laterally spurred. Standard ‘normally’ developed; entire; not sericeous. Keel about equalling the wings; not long-acuminate/beaked (blunt); neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); in ours, white, or yellow, or pink, or yellow and pink, or white and pink; deciduous; non-accrescent. Petals clawed (the standard shortly so). Androecial members definite in number. Androecium 10. Androecial sequence determinable, or not determinable. Androecial members free of the perianth; all equal, or markedly unequal; coherent (basally, into a tube); 1 - adelphous, or 2 - adelphous (the tube partially or completely split, and the vexillary stamen either free, or connate less high). The staminal tube free from the keel petals. Androecial members 1 -whorled (although diplostemonous). Androecium exclusively of fertile stamens. Stamens 10; all more or less similar in shape; diplostemonous; both opposite and alternating with the corolla members. Anthers separate from one another, or connivent; all alike; dorsifixed, or basifixed (? — Dunlop et al disagree with Wheeler et al on this); versatile, or non-versatile; dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. Pollen shed as single grains (tricolporate). Fertile gynoecium present. Gynoecium 1 carpelled. The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium monomerous; of one carpel; superior. Carpel stylate; apically stigmatic. Style ‘long’. Style hairy but not bearded (hairy towards the base only). Stigmatic tissue terminal. Carpel (1–)2–8 ovuled (in ours). Placentation marginal. Gynoecium median (the placenta posterior, on the ventral suture). Ovary sessile. Ovary summit hairy, the hairs not confined to radiating bands (densely hirsute). Stigmas capitate. Ovules pendulous to ascending; biseriate; arillate, or non-arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit 6–20(–32) mm long (in ours); sessile; non-fleshy; hairy, or not hairy; not spinose. The fruiting carpel indehiscent; a loment. Pods somewhat elongated, or much elongated; not triangular; curved (falcate), or straight to curved; not becoming inflated; more or less flat, or somewhat compressed; regularly constricted between adjacent seeds; transversely septate between the seeds, or not transversely septate; wingless. Fruit 1 celled; 1–8 seeded. Seeds reniform; endospermic, or non-endospermic; not mucous; strongly compressed; small; non-arillate (? — Wheeler et al intimate a rim-like aril). Cotyledons 2; accumbent. Embryo curved, or bent (the radicle inflexed). Testa non-operculate. Micropyle zigzag, or not zigzag. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Nitrogen-fixing root nodules present. Aluminium accumulation not found. Photosynthetic pathway: C₃.

Geography, cytology, number of species. Native of Australia. 2n=22. A genus of 12 species; 1 species in Western Australia.