Diastatea, Scheidw., Allg. Gartenzeitung (Otto & Dietrich)

Johnson, Elizabeth P. & Ayers, Tina J., 2022, Molecular Phylogeny and Taxonomic Revision of the Genus Diastatea (Campanulaceae: Lobelioideae), Systematic Botany (Basel, Switzerland) 47 (1), pp. 61-84 : 71

DIASTATEA Scheidw., Allg. Gartenzeitung (Otto & Dietrich) 9: 396. 1841.

TYPE: Diastatea virgata Scheidw.

Herbaceous annuals. Roots branching, fibrous. Stems ascending to erect, simple to highly branched, often minutely winged, green to often purple below, glabrous to pubescent, especially on wings. Leaves alternate, cauline, petiolate or sessile; lowermost blades smaller and often broadly ovate or round, increasing in size upward; middle and upper blades broadly ovate to narrowly elliptic or linear; bases often decurrent; apex round to acuminate; margins regularly or irregularly serrate, sometimes serrulate, crenate, or erose, the teeth tipped with white or purple thickened callosities, or reduced to marginal callosities; glabrous, or the margins, veins, and pseudo-petioles (if present) ciliate-pubescent. Inflorescences weakly to strongly secund terminal raceme with few to many flowers; bracts leaf-like, becoming smaller and linear distally, ascending to appressed. Flowers resupinate at anthesis; pedicels filiform, ebracteolate, ascending, glabrous to scabrous, green to purple, elongating in fruit, the distal portion often bent toward stem so that mature fruit is erect; hypanthium either obconic or somewhat flattened and disc-shaped in flower, sometimes enveloping lower portion of capsule in fruit, glabrous to minutely scabrous; calyx lobes subequal to equal, narrowly triangular, linear, or narrowly elliptic, apex acute, margins entire or with 1–2 pairs of teeth, glabrous or ciliate; corollas distinctly bilabiate, white to purplish-blue, glabrous; tube broadly to narrowly cylindrical or funnelform, with or without a gibbous projection at base on ventral side, not cleft dorsally, or with slight cleft such that dorsal sinus exceeds the lateral sinuses; dorsal lobes two, broadly triangular or distal portion elliptic to obovate with a claw attaching to deltoid base; ventral lobes three, rounded to oblong with nectar guides at throat; filaments white to purple, connate distally up to half their length, distinct at base and adnate to corolla; anther tube exserted, dark purple or striped with tan to white at anther margins, usually with a white downy covering, sometimes with stiff hairs on back of dorsal anthers, apex of two shorter ventral anthers with two large triangular trichomes attached interior to additional smaller ones; pollen white to yellow, ovoid when dry; ovary superior in flower, bilocular, placentation axile; style purple and tipped with a ring of white trichomes before splitting into two recurved stigmatic lobes. Fruit a capsule, superior to apparently half-inferior due to expanding hypanthium, glabrous, enclosed in persistent shiny, hyaline corolla tube, dehiscing loculicidally by apical valves; seeds ellipsoid, 0.4–0.6 mm long, orange to brown, smooth and shiny with faint striations.

Notes —Michael Josef Francois Scheidweiler collected and proposed the name for Diastatea in 1841 based upon the species D. virgata Scheidw. ( Otto and Dietrich 1841) . The etymological origin stems from the Greek word diastatos, which means “having extension, severed, disunited, or torn by faction” ( Quattrocchi 2000). The characters he felt defined the genus included the free (superior) ovary and capsule, as well as the entire corolla tube and the manner in which it enveloped the mature capsule. In his discussion on the plant’ s merits as an ornamental in the greenhouses of the Belgian king, he alluded to its flowering time; he said that it would be a pleasant addition to the Lobelia currently under cultivation, because although it didn’ t grow as large as them, it bloomed in the fall when they had stopped blooming ( Otto and Dietrich 1841).