Amsinckia Lehm.

Scientific Description

Common name. Yellow burrweeds. Family Boraginaceae.

Habit and leaf form. Herbs; without essential oils. Autotrophic. Annual. Leaves basal and cauline. Plants with a basal concentration of leaves; to 1 m high. Helophytic, or mesophytic, or xerophytic. Leaves minute to medium-sized; alternate; sessile; non-sheathing; not gland-dotted; simple; epulvinate. Leaf blades dorsiventral, or isobilateral; entire; flat; linear to lanceolate; linear, or ovate, or obovate; cross-venulate; sub- cordate, or cuneate at the base. Mature leaf blades adaxially pubescent; abaxially pubescent. Leaves without stipules. Leaf blade margins entire (always?). Leaves without a persistent basal meristem. Leaf anatomy. Hairs present (with a broad base). Urticating hairs absent. Stem anatomy. Secondary thickening developing from a conventional cambial ring.

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

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes. Inflorescences simple. The terminal inflorescence unit cymose (coiled at first). Inflorescences terminal; scorpioid, with flowers densely arranged in 2 rows; not pseudanthial. Flowers pedicellate to sessile; bracteate, or ebracteate; bracteolate; small; regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present, or absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; lobed. Calyx lobes markedly longer than the tube. Calyx imbricate, or open in bud, or valvate. Degree of gamosepaly, maximum length joined/total calyx length less than 0.25. Calyx regular; neither appendaged nor spurred; persistent; accrescent. Calyx lobes elliptic, or ovate. Corolla present; 5; 1 -whorled; appendiculate (with 5 saccate scales in the throat), or not appendiculate; gamopetalous; lobed. Corolla lobes markedly shorter than the tube. Corolla imbricate, or contorted; tubular; regular; glabrous abaxially; hairy adaxially (scales hairy), or glabrous adaxially; yellow to orange. Corolla lobes oblong (to square). Fertile stamens present. Androecial members definite in number. Androecium 5. Androecial members unbranched; adnate (to the corolla); all equal; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5. Staminal insertion midway down the corolla tube, or in the throat of the corolla tube. Stamens all inserted at the same level; tips becoming exserted, or remaining included; all more or less similar in shape; isomerous with the perianth; oppositisepalous; filantherous (to subsessile), or with sessile anthers. Anthers all alike; dorsifixed to basifixed; dehiscing via longitudinal slits; introrse; tetrasporangiate. Gynoecium 2 carpelled. The pistil 4 celled (usually), or 2 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular (4-lobed); 2 locular (‘really’, but rarely ostensibly so), or 4 locular (ostensibly, via false septa). Locules secondarily divided by ‘false septa’. Gynoecium median; stylate. Styles 1; simple; from a depression at the top of the ovary; ‘gynobasic’, or apical; not becoming exserted; hairless. Stigmas 1; 2 - lobed; capitate. Placentation axile to basal. Ovules differentiated; 2 per locule (i.e. per true locule), or 1 per locule (per cell, the gynoecium separating into one-ovuled portions); horizontal to ascending; epitropous; non-arillate; anatropous, or hemianatropous.

Fruit and seed features. Fruit aerial; non-fleshy; not spinose; a schizocarp. Mericarps 4; comprising achenes, or comprising nutlets, or comprising drupelets; dull (and tuberculate-rugose). Seeds endospermic, or non-endospermic. Cotyledons 2. Embryo straight, or curved.

Special features. Corolla tube straight.

Etymology. After Wilhelm Amsinck (1752–1831), burgomaster of Hamburg, who developed the botanical gardens of that city.