Ruellia species, 1753

Silva, Marcos José Da, 2022, Ruellia scarlatina, a new name for the sixty-year-old but misunderstood Ruellia capitata Rizzini (Acanthaceae), Phytotaxa 547 (1), pp. 55-65 : 60

Key to Ruellia species with red flowers occurring in Goiás

1. Flowers in lax or congested terminal thyrses; corolla infundibuliform always with curved lobes; bracteoles> 1 cm long, foliaceous, covered with non-glandular and glandular trichomes ........................................................................................................................2

- Flowers usually in compound dichasia or monochasia, both long-pedunculate, solitary, in pairs(or even three), or in fascicles in the leaf axils; corolla bilabiate or tubiform with straight or slightly curved lobes; bracteoles, when present, <5 mm long, with nonglandular trichomes ............................................................................................................................................................................4

2. Plants glabrous; leaves always opposite, scabridulous on both surfaces, trichomes unicellular; thyrses glomeruliform 4-sided; bracts lanceolate, with sessile glandular trichomes on lower surface; bracteoles ovate; flowers subsessile; calyx foliaceous with subequal lobes; cystoliths conspicuous, seeds 7 or 8 ............................................................................ Ruellia scarlatina ( Fig. 5 , B)

- Plants indumented; leaves opposite and whorled on the same individual, indumented by velutinous or villous and pluricellular trichomes; thyrses elongated; bracts elliptic or elliptic-obovate covered by glandular stipitate trichomes on both surfaces; bracteoles oblanceolate or spatulate; flowers conspicuously pedicellate, calyx with equal lobes; cystoliths inconspicuous; seeds 3 or 4.......... ............................................................................................................................................................................................................3

3. Leaves sessile, elliptic-obovate with apex obtuse, villous and not whitish on both surfaces; secondary veins prominent on abaxial surface, straight; branches densely villous; capsules densely villous ................................................ Ruellia angustior ( Fig. 3 , F–H)

- Leaves petiolate, broadly elliptic or ovate, with apex shortly acuminate, densely velutinous-whitish on both surfaces; secondary veins impressed on abaxial surface, curved; branches densely velutinous; capsules glabrous or glabrescent .................................... ......................................................................................................................................................... Ruellia adenocalyx ( Fig. 3 , A–E)

4. Flowers in monochasial or compound dichasia, long pedunculate; seeds 8–16 ................................................................................5

- Flowers solitary, in pairs of (or even three) fascicles, sessile; seeds 4–6 ............................................... Ruellia densa ( Fig. 4 , C, D)

5. Corolla ventricose, slightly bilabiate, with erect or ascending lobes and yellow throated internally; stamens weakly didynamous; seeds 10–16 ....................................................................................................................................... Ruellia brevifolia ( Fig. 4 , A, B)

- Corolla not ventricose, conspicuously bilabiate, with lobes conspicuously curved and throat red or orange internally; stamens conspicuously didynamous; seeds 8–12.............................................................................................................................................6

6. Subshrubs erect; leaves indumented, with apex and base obtuse; flowers in monochasia; corolla hypocrateriform, slightly bilabiate; seeds 10–12, uniformly indumented.......................................................................................................... Ruellia elegans ( Fig. 5 , B)

- Subshrubs with supporting branches; leaves glabrous with apex acuminate and base slightly amplexicaulous; flowers in longpedunculate dichasia; corolla tubular conspicuously bilabiate; seeds 8, indumented on margins.................... Ruellia amplexicaulis

Figures

FIGURE 3. Ruellia adenocalyx M.J. Silva. A–E. A. Habit; B. Portion of the stem showing the phylotaxy; C. Detail of the inflorescence, note the bracts elliptical; D. Part of the inflorescence after the fall of the corolla, note the elliptical bracts with glandular trichomes; E. Flowers in lateral view, note the corolla lobes recurved. R. angustior F–H. F. Flowering branch, note the long inflorescence with spatulate bracts;G. Portion of the stem showing the phylotaxy and the appearance of axillary inflorescences, and H. Flowers in lateral view, note the corolla lobes recurved. Photographs by M. J. Silva.

FIGURE 4. Ruellia brevifolia A and B. A. Flowering branch, note the lax inflorescence; B. Flower, note the corolla ventricose. R. densa. C-D. C. Flowering branch, note the corolla tubular with lobes straight; D. Corolla in frontal view. Photographs by I. S. Santos.

FIGURE 5. Ruellia elegans A and R. scarlatina B. In A, note the membranaceous leaves and the inflorescence long pedunculate, in B, note the inflorescence compacted, similar toa head and the bracteoles elliptical with glandular trichomes.A. Photographs from iNaturalist website (iNaturalist.org), and B, by M. J. Silva.