Trifolium L.

Scientific Description

Family Papilionaceae. Trifolieae.

Habit and leaf form. Herbs; not resinous. Annual, or biennial, or perennial. Leaves cauline. Plants with neither basal nor terminal concentrations of leaves. Helophytic, or mesophytic. Leaves small to medium-sized; alternate; spiral; ‘herbaceous’; not imbricate; petiolate; non-sheathing; not gland-dotted; compound; epulvinate; unifoliolate (rarely), or ternate (mostly), or pinnate, or palmate. Leaves usually pinnately trifoliolate, or palmately trifoliolate. Leaflets (1–)3, or 5–7 (rarely); not stipellate; pulvinate, or epulvinate; flat. Leaf blades dorsiventral. Leaves with stipules. Stipules intrapetiolar; adnate to the petiole; free of one another, or concrescent; persistent. Leaf blade margins minutely dentate (denticulate). Leaves without a persistent basal meristem. Stem anatomy. Nodes tri-lacunar, or penta-lacunar. Secondary thickening absent, or developing from a conventional cambial ring.

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

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in racemes, or in spikes, or in heads. The terminal inflorescence unit racemose. Inflorescences terminal, or axillary (mostly); few- to many-flowered capitate or spicate racemes; with involucral bracts (comprising stipules), or without involucral bracts; pseudanthial, or not pseudanthial. Flowers pedicellate to sessile; bracteate (usually), or ebracteate; ebracteolate (nearly always), or ebracteolate (T. ornithopodioides); small to medium-sized; very irregular; zygomorphic; not resupinate. The floral asymmetry 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 developing a gynophore, or 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; five lobed; imbricate, or valvate; exceeded by the corolla; campanulate, or tubular; regular to unequal but not bilabiate (with five subequal lobes), or bilabiate; non-fleshy; persistent; accrescent (becoming inflated), or non-accrescent; with the median member anterior. Epicalyx absent. Corolla present; 5; 1 -whorled; appendiculate, or not appendiculate. Standard appendaged, or not appendaged. Corolla partially gamopetalous, or gamopetalous. 2–5 of the petals joined (including the two ventral petals connivent to form the ‘keel’). The joined petals anterior, or anterior and posterior. The wings of the corolla adherent to the keel, or free from the keel; not laterally spurred. Standard ‘normally’ developed. Keel about equalling the wings, or conspicuously exceeding the wings (mostly); not long-acuminate/beaked; neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); white, or cream, or yellow, or red, or pink, or purple; (or some members) persistent. Petals clawed. Androecial members definite in number. Androecium 10. Androecial sequence determinable, or not determinable. Androecial members adnate (the base of the tube adnate to the claws of the anterior petals); all equal, or markedly unequal; coherent (nine of them with filaments basally united to form an adaxially split tube); 2 - adelphous (1+9, the vexillary member free of the tube); 1 -whorled. Androecium exclusively of fertile stamens. Stamens 10; all more or less similar in shape, or distinctly dissimilar in shape; (sub-) diplostemonous; both opposite and alternating with the corolla members. Filaments filiform, or club-shaped (distally, beyond the tube). Anthers separate from one another, or connivent; all alike; dorsifixed; versatile; dehiscing via pores, or dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. 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 straight, or curved, or hooked, or bent. Style glabrous. Stigmatic tissue terminal, or oblique. Carpel 1–5(–7) ovuled. Placentation marginal. Gynoecium median. Ovary sessile to stipitate. Ovules pendulous to ascending; biseriate; arillate, or non-arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit subterranean (sometimes), or aerial; non-fleshy; not spinose. The fruiting carpel indehiscent (membranous, rarely leathery); a legume (more or less, but not dehiscent). Pods globose to somewhat elongated (ovoid to ellipsoid or cylindric, often concealed within the calyx tube); not triangular; straight; somewhat compressed, or terete. Fruit 1 celled. Dispersal unit the seed, or the fruit. Fruit 1–2(–3) seeded. Seeds endospermic, or non-endospermic; not mucous; small; non-arillate. Cotyledons 2; accumbent. Embryo chlorophyllous; (in-) curved, or bent (the radicle inflexed?). Testa non-operculate. Micropyle zigzag, or not zigzag. Seedling. Germination phanerocotylar.

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

Geography, cytology, number of species. Native of Australia and adventive. 35 species in Western Australia.

Additional comments. Numerous queries (e.g. re anthers) need following up.