Dichasium

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Related to dichasia: dichasium, Racemes

dichasium

[dī′kā·zhē·əm]
(botany)
A cyme producing two main axes from the primary axis or shoot.

Dichasium

 

the inflorescence in plants of the cymose type. The primary axis in dichasium ends in a single apical flower. From the two opposite axils under that flower two lateral branches develop that exceed the primary axis in height and also end in flowers, which blossom later. On each of them in turn, two more lateral branches develop that overtake them in height and end in apical flowers, which blossom still later, and the process continues. Dichasium is typical for many plants of the family Caryophyllaceae and others. Sometimes branching and growth in dichasium is disturbed somewhat and inflorescences form that outwardly do not resemble dichasium (as in so-called false whorls in plants of the family Labiatae).

References in periodicals archive ?
However, these two species differ in a number of important diagnostic traits, mainly regarding the order of branching and the position of the dichasia (see above).
Habit Shrubs to 5 m tall (exceptionally to 10 + trees to 40 m tall m tall) Stipule margin laciniate entire Leaf blade membranaceous, margin chartaceous, plane margin revolute Number of lateral 8 to 11 4 to 8 veins on each side Branching, 2-forked, axillary to the 4 to 6-forked, mostly on position and size distalmost leaves, to 1 defoliate branches, to 3.5 of dichasia x 1 cm x 2.5 cm Length of 2.5-3.5 mm 3-8 mm dichasial peduncle Calyx, corolla 4 or 5 5 and androecium merosity Sepal margins erose entire Samara two-celled, one-seeded, one-celled, one-seeded, 16-19 x 5-6 mm, 20-28 x 7.5-17 mm, higher higher order veins order veins prominent inconspicuous Geographic Colombia (Boyaca), N Venezuela (Aragua, DF, distribution and 2740-2950 m Vargas, Miranda Yaracuy), elevation below 1000 m.
Species similar to Psittacanthus lasianthus, from which it differs by the sympodial, densely puberulous, three-angled stems, ternate leaves, terminal dichasia, perfoliate bracts, a neck-bearing, not inflated corolla densely laciniate on its outer surface and a triangular, ligule on the inside of each petal, a ring-like nectary, and a micropapillose stigma versus percurrent, glabrous, circular stems, paired leaves, axillary dichasia, not perfoliate bracts, a neck-lacking, inflated corolla without laciniae on its outer surface and a finger-like ligule on the inside of each petal, a 4-lobed nectary, and a smooth stigma in P.
Inflorescences formed by one terminal and two subterminal (lateral) double dichasia (triads), rarely with the terminal flower of the dichasium aborted resulting in the atypical formation of dyads; internodes 5-16 mm long.
Roy), the axillary bud of the prophylls generates one flower; consequently, the florescence is formed by dichasia. The cymose branching may repeat itself from the axillary bud of the prophylls in each flowering axis of the following order, and then some partial florescences (cymes) may show a complex structure (Rua, 1999).
Solitary flowers, Stebbins (1973, 1974) pointed out, are usually derived in primitive families; as an example, the solitary flower of Zygogynum is the exception in Winteraceae, in which all other taxa have axillary cymes or dichasia. Rickett (1944) favored a dichasium as the ancestral type of inflorescence, while Stebbins (1974) argued convincingly for a leafy cyme being most primitive, based on its correlation with other primitive character states in the more basal angiosperm families.
Inflorescence terminal or axillary, solitary (Desfontainia) or cymose (usually a dichasia), rarely spikes, racemes and panicles.