A Revision of Coleus (Labiatae) in Sri Lanka (Ceylon)

A Revision of Coleus (Labiatae) in Sri Lanka (Ceylon)Author(s): L. H. CramerSource: Kew Bulletin, Vol. 32, No. 3 (1978), pp. 551-561Published by: Springer on behalf of Royal Botanic Gardens, KewStable URL: http://www.jstor.org/stable/4109658 .

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A revision of Coleus (Labiatae) in Sri Lanka

(Ceylon) L. H. CRAMER*

Summary. The genus Coleus in Sri Lanka is critically reviewed. Its delimitation from Plectranthus is considered and upheld for the Sri Lankan species. I I species and 2 varieties are recognized, including two new species C. grandis and C. kanneliyensis. A key to the species and descriptions of new taxa are provided and the combination Coleus zeylanicus made.

INTRODUCTION

The generic limits between the allied genera Plectranthus and Coleus have become highly controversial in the palaeotropics. Investigation into this problem is all the more desirable in Asia, where the present knowledge of these genera is as yet incomplete. Especially is this so in Sri Lanka which has seven species in Plectranthus, and eleven usually placed in Coleus.

In the course of reinvestigating the relationship of these genera an attempt has been made to ascertain whether any valid characters delimit the one genus from the other as they occur in Sri Lanka, according to their general acceptance.

DIscUSSION

In recent years the separation of Plectranthus and Coleus, traditionally treated as distinct genera, has come under re-appraisal, especially among taxonomists of the West African flora, where the two genera show over- lapping characters, especially in their stamens and calyces. Morton (1962), for example, states: 'The difficulties centre around defining generic limits and around the large number of closely allied species many of which are inadequately known from scanty herbarium material.'

The chief difficulty in delimiting Coleus from Plectranthus lies in the fact that they are closely related in a complex with other genera, viz. Solenostemon, Englerastrum, Neomuellera and Burnatastrum, and there is no consensus of opinion about the delimitation of them. For a discussion on Englerastrum & Coleus, see Cramer

(1975). Loureiro (1790) and Bentham (1832, 1848), originally recognized the

generic status of Coleus, emphasizing its distinctive character of the fusion of stamens. Brown (18io) and Blume (1826) did not consider this character of sufficient importance, and recognized only the genus Plectranthus.

Following Brown and Blume, modern taxonomists of West Africa uphold only Plectranthus, and extend it to include all Coleus-like species. Morton (1962), Launert (1968), and Codd (I97I), have questioned the constancy of the staminal sheath as a safe, distinguishing character of Coleus. Morton has circumscribed his enlarged concept of Plectranthus thus: 'Calyx bilabiate ... upper tooth of calyx decurrent on the tube, broadly ovate but not exceeding the other teeth; inflorescence paniculate, if spicate then narrow or lax and

Accepted for publication 26 April 1977. * Flora of Ceylon Project, Botanic Gardens, Peradeniya, Sri Lanka. 551



552 KEW BULLETIN VOL. 32(3)

without large bracts.' This excludes the type species of Coleus, C. amboinicus, where the upper tooth of the calyx is not decurrent on the tube and its length variable (often longer than the other teeth).

Launert, while not agreeing with Morton's definition, compromises by including in Plectranthus 'species in which the superior tooth of the calyx is both longer than the other teeth and not conspicuously decurrent on the tube.' (1968: 296). This might be a good compromise if not for the character of the fused stamens in C. amboinicus and the other Sri Lankan species of Coleus, as is explained below.

Keng (1969) accepted the fusion of stamens as a stable distinguishing character of Coleus in Malesia, and tentatively considers it as distinct from Plectranthus.

S. T. Blake (1972), too, accepts the fusion of stamens as a valid distinguishing character of Coleus in Australia.

As for the Sri Lankan species, I would disagree with Morton that the fusion of stamens in Coleus is entirely an arbitrary character. Examination of 40 specimens of the eleven different species of Coleus from various localities showed the filaments to be fused into a tubular sheath. In those of ten species the filaments were observed to be fused for more than half their length (Fig. I G, H); in those of another the filaments were observed to be fused for somewhat less than half their length (Fig. I J). Similar examination of 18 specimens of the six species of Plectranthus at present occurring here showed the completely free nature of the filaments. Consistent with Loureiro's analysis the fusion of stamens is a very distinctive character of Coleus as it exists in Sri Lanka.

These studies have borne out that the fusion of stamens in Coleus species is best observed in fresh material. Pressing can at times cause a tearing of the staminal sheath towards the base.

Secondary characters which in a lesser degree establish the distinctness of Coleus from Plectranthus are those of the calyx and of the floral leaves.

The peculiarity of the calyx in the two genera is the upper lip. In Coleus it is always I-lobed; in Plectranthus it is either 3- or I-lobed, or the limb may be subregular. More important is the continuity or discontinuity of the upper lip. In Coleus the upper lip is decurrent (or winged) on the calyx tube (Fig. I E, F). A striking anomaly of this condition is in C. amboinicus. (Fig. I D). Here the upper lip is continuous with the calyx tube, as in nearly all species of Plectranthus. A modified form of the latter condition obtains in two

species of Plectranthus-viz. P. glabratus and P. subincisus-where the upper lip is subdecurrent on the calyx tube.

In Coleus the floral leaves before anthesis are in closely imbricate rows; (Fig. I A-C); in Plectranthus (with the exception of P. gardneri and P. coetsa), these are laxly arranged.

In my opinion, the fusion of stamens in Coleus, in combination with these two secondary characters, forms a sufficient basis for circumscribing Coleus as a valid genus distinct from Plectranthus, at least as far as our species are concerned.

The results obtained in this study need to be supplemented by further data from all the palaeotropical regions where the genus occurs. Although Morton's cytotaxonomic studies on the West African species did not yield useful information on this problem of generic delimitation, further cytological



A REVISION OF COLEUS (LABIATAE) IN SRI LANKA 553

data and palynology studies could especially shed further light on it. This treatment of Coleus vs. Plectranthus, therefore, is by no means conclusive, least of all, authoritative. In spite of its limited scope it is hoped the effort will prove useful in any subsequent monograph of wider dimensions for Asia. I have seen all the cited specimens, unless otherwise indicated; distributions will be given in the forthcoming account for the Revision of the Flora of Ceylon.

FIo. I. Floral parts of Coleus spp. Floral leaves: A, C. amboinicus, x 5; B, C. malabaricus, x 4; C, C. grandis, x I. Calyces: D,- C. amboinicus, x 8; E, C. inflatus, x 4; F, C. grandis, X 3. Stamens & style: G, C. amboinicus, x 4; H, C. barbatus, x 4; J, C. zeylanicus, x 6.

KEY TO THE GENERA COLEUS & PLECTRANTHUS IN SRI LANKA

Stamens fused into a sheath around style; upper lip of calyx usually decurrent or subdecurrent on tube; members of one row of young floral leaves closely imbricate with those of the next . . . . . . Coleus

Stamens free from each other; upper lip of calyx usually continuous with tube; members of one row of young floral leaves laxly imbricate with those of the next ........... Plectranthus

Coleus Loureiro, Fl. Cochinch. 2: 358, 372 (1790).

All the indigenous species are gregarious, two of them, C. barbatus and C. mollis often growing in dominant stands. C. barbatus and C. amboinicus (if




growing wild) keep to typically xeric habitats in ledges and crevices of exposed, rocky outcrops, chiefly in the dry lowlands. C. elongatus, too, grows in rocky situations, but the habitat is mesic in the intermediate zone.

Except for C. barbatus, C. grandis and C. elongatus, the wild species prefer shade and thrive as part of a wet, evergreen or montane forest undergrowth, occurring either close to or along watercourses. Here moderately dense shade prevails as a result of which the leaf laminae are spread out divaricately on markedly long petioles, whilst the upper part of the stems and petioles are fairly conspicuously coloured (pinkish-red or maroon). As a result of the excess water of their substratum the stems and petioles of these species are succulent, though the leaves are membranous.

KEY TO THE SPECIES OF COLEUS IN SRI LANKA

I. Upper lip of calyx continuous with or subdecurrent on the tube: 2. Verticels dense, spicate; stamens much exserted beyond the lower lip

of corolla; upper lip of calyx continuous with the tube I. C. amboinicus

2. Verticels lax; stamens included in the lower lip of corolla; upper lip of calyx subdecurrent on the tube:

3. Leaves uniformly green; corolla limb mauvish-pink; plants perennating by root tubers ..... 2. C. rotundifolius

3. Leaves variegated; corolla limb blue; plants perennating by a rootstock . ........ 3. C. scutellarioides

I. Upper lip of calyx distinctly decurrent on the tube: 4. Adult stem densely hirsute; young floral leaves silvery-grey; calyx

tube hirsutulous-annulate within: 5. Decumbent or shortly erect herb; leaves not more than 4'7 cm

broad; racemes to 33 cm long; corolla not more than 1.7 cm long; nutlets globose . . . . . . 4. C. barbatus

5. Shrub; leaves more than 4'7 cm broad; racemes to 56 cm long: corolla more than 2.0 cm long; nutlets subtrigonous, oblong- orbicular . .......... 5. C. grandis

4. Adult stem glabrous, puberulous or with minute hairs; young floral leaves pale green, or faintly purplish-red; calyx tube exannulate within:

6. Stem acutely 4-angular; leaves membranous, acuminate or acute; cymes in branched thyrses; nutlets subtrigonous, ovoid-oblong, biconvex and orbicular; plants generally not or faintly aromatic:

7. Stem tumid above nodes, usually mottled dull purple on the sides; inflorescence branches in verticels; nutlets dorsally ribbed; shrubs or undershrubs:

8. Angles of stem ? winged; young stem and inflorescence axis glabrous, puberulous, or hirtellous with gland-tipped hairs; floral leaves deciduous:

9. Corolla tube weakly sigmoid, the lower lip laterally com- pressed and keeled; upper lip uniformly lavender

6. C. inflatus 9. Corolla tube distinctly sigmoid, the lower lip navicular;

upper lip streaked bluish-violet above:




10. Inflorescence axis ending in a cyme; inflorescence, including calyx, with eglandular hairs; lateral calyx lobes at anthesis ovate-triangular; nutlets oblong- orbicular, dorsally 3-ribbed 7. C. malabaricus

Io. Inflorescence axis ending in an aborted bud or flower; inflorescence, including calyx, with gland-tipped hairs; lateral calyx lobes at anthesis truncately semi-lunar; nutlets narrowly ovoid, dorsally 4-5- ribbed ...... 8. C. kanneliyensis

8. Angles of stem plain; young stem and peduncles with dense short indumentum; floral leaves ? persistent 9. C. mollis

7. Stem uniformly thickened, uniformly green on sides; inflorescence branches secund; nutlets dorsally smooth; herbs

10. C. elongatus 6. Stem obtusely 4-angular; leaves fairly thick, rounded or obtuse;

cymes in verticels; nutlets globose; plants strongly aromatic I I. C. zeylanicus

I. C. amboinicus Lour., Fl. Cochinch. 2: 372 (1790). Type: Rumphius Icon. in Herb. Amb. 5: t. I02, f. 2 (I750) (lectotype).

C. aromaticus Benth. in Wall., P1. As. Rar. 2: 15 (1831). Type: India, Patna, Wall. Num. List 2730 (holotype, K-WALL.)

Plectranthus amboinensis Spreng., Syst. 2: 690 (1825). Type: based on Coleus amboinicus Lour.

P. aromaticus (Benth.) Roxb., Fl. Ind. ed. 2, 3: 22 (1832).

2. C. rotundifolius (Poir.) A. Chev. & Perr. in A. Chev., Veg. Util. Afr. Trop. Frang. I: IoI (1905), excl. C. dysentericus Baker (1895). Type: Mauritius, Commerson s.n., in Hb. Desfont. (holotype, not seen).

Germania rotundifolia Poir. in Lam., Encycl. Suppl. 2: 763 (1788). Plectranthus tuberosus BI., Bijdr.: 838 (1826). Type: Java, Blume s.n. (holotype

& isotype, L). Coleus tuberosus (BI.) Benth., Lab. Gen. & Sp.: 59 (1832). Coleus parviflorus Benth. in DC., Prodr. 12: 72 (1848). Type: India, Wight

2512, in Hb. Wight (holotype, K; isotype, E).

3. C. scutellarioides (L.) Benth. in Wall., Pl. As. Rar. 2: 16 (1830), Lab. Gen. & Sp. 53 (1832), & in DC., Prodr. 12: 73 (1848). Type: described from Amboina.

Ocimum scutellarioides L., Sp. Pl. ed. 2: 834 (1763).

a. var. scutellarioides Coleus blumei Benth., Lab. Gen. & Sp.: 56 (1832). Type: Java (not seen).

b. var. crispipilus (Merr.) Keng in Gard. Bull. (Sing.) 24: 56, I969. C. crispipilus Merr. in Phillip. J. Sci. (Bot.) 5: 382, 190.

4. C. barbatus (Andr.) Benth. in Wall., P1. As. Rar. 2: 15 (I831), Lab. Gen. & Sp. 49, 177 (1832), & in DC., Prodr. I2: 71 (I848), excl. syn. Germaniaforskohlii Poir. Type: the illustration in Bot. Rep. 9: t. 594 (1809).




Plectranthus barbatus Andr., Bot. Rep. 9: t. 594 (1809). [Coleus forskohlii sensu Briq. in Pflanzenfam. 4 (3a): 359, I897; Alst. in

Trimen, Handb. Fl. Ceyl. 6 (Suppl.): 236, I93I; Mukerj. in Rec. Bot. Surv. Ind. 14 (I): 53, (1940)]

5. C. grandis Cramer, sp. nov., C. barbato (Andr.) Benth. affinis, sed habitu fruticoso, foliis maioribus apice acutis, racemis corollisque longioribus atque nucularum forma differt. Typus: Sri Lanka, Sita Eliya, Cramer 3869 (holotypus, PDA; isotypi, K, US).

Frutex usque 1.75 m altus. Caules subquadrangulares, dense hirsuti, pilis glandulis oleosis sessilibus interpositis. Folia ovato-ovalia usque late ovata, 6-23 x 4.5-19 cm, basi truncata, apice acuta, crasse crenata, utrinque hispida; petiolus 0o5-6 cm longus, supra leviter sulcatus. Inflorescentiae racemosae; racemi simplices, erecti, 26-56 cm longi; pedunculi rigidi; verticillastri laxi, Io-flori. Foliafloralia late ovata, usque I -2 x o09 cm, apice acuminata. Pedicelli 5-7 mm longi, rigide declinati, viscoso-hispidi. Calyx late campanulatus, glandulis oleosis sessilibus notatus; tubus 3'5-4 mm longus, Io-nervatus, intus pilis capite glanduligeris dense hispidule annulatus, extra pills capite glanduligeris hispidulus; labium superius erectum, late ovatum, 4-7 x 4 mm, extra puberulum, apice aetate reflexum; labii inferioris lobi ovato-lanceolati, laterales usque 2"5

mm longi, centrales 3-3'5 mm longi, longe acuminati. Corolla

2'2-2"6 cm longa, valde purpureo-

caerulea, extra olei guttulis notata; tubus I1-12 mm longus, superne dilatatus, lateraliter compressus, inferne angustatus; labium superius erectum, ovatum, inferius stipitatum, ovato-oblongum, I "5-2 cm longum, naviculatum. Stamina declinata, in labio inferiore corollae inclusa; filamenta glabra; thecae reniformes. Discus anterius linguae ad instar porrectus. Stylus glaber. Nuculae orbiculari-oblongae, 2o x IX'75 mm, subtrigonae, supra leviter 3-sulcatae, glabrae, nigrae, nitidae. (Fig. 2).

SRI LANKA. C. Province: Nuwara Eliya District: Ohiya, by rail track near station, Balakrishnan 482 (PDA, US); ibid., borders of Eucalyptus plantation, beside railway station, Cramer 4437 (E, K, L, PDA, US), Sita Eliya, Cramer 3869 (PDA, holotype; K, US, isotypes).

Originally cultivated as a hedge plant it is now becoming established along roadside watercourses and drains in the highlands and uplands. It has never been known in the wild, nor is there any information on how it originated in cultivation. The inflorescence has a musky odour; in full bloom it is conspicuous and is a pretty sight. Cattle are observed not to eat the

plant. Flowering: September-February. According to Mr. Mathew, this plant has been observed growing in

cultivation in Tropical Africa also, but has not so far been described.

6. C. inflatus Benth., Lab. Gen. & Sp.: 58 (1832), & in DC., Prodr. 12:

78 (1848). Type: Ceylon, Macrae s.n., in Hb. Benth. (holotype, K). C. benthamianus Arn., Pug. P1. Ind. Ord. 36 (1836). Type: Ceylon, Graham

s.n. (type, not seen).

7. C. malabaricus Benth. in Wall., P1. As. Rar. 2: I6 (1831), Lab. Gen. & Sp. 47 (1832), & in DC., Prodr. I2: 76 (I848). Type: India, Travancore, Wall. Num. List 2735A, in Hb. Madr. (holotype, K-WALL.)




FIG. 2. Coleus grandis. A, flowering branch, x ix; B, calyx, X 24; C, corolla, x if, D, stamens & style, X 4; E, seed, x 4.




a. var. malabaricus

C. macraei Benth., Lab. Gen. & Sp.: 58 (1832), & in DC., Prodr. 12: 77 (I848). Type: Ceylon, Macrae s.n., in Hb. Benth. (holotype, K).

C. walkeri Benth. in DC., Prodr. 12: 77 (1848). Type: Ceylon, Walker s.n., in Hb, Benth. (holotype, K).

b. var. leptostachys (Benth.) Hook. f., Fl. Brit. Ind. 4: 625 (1885). Type: Ceylon, Walker s.n., in Hb. Benth. (holotype, K).

C. leptostachys Benth. in DC., Prodr. 12: 77 (1848).

8. C. kanneliyensis Cramer & Balasubramaniam, sp. nov., C. malabarico Benth. affinis sed inflorescentiae axibus gemma abortiva terminatis, nuculis anguste ellipsoideis et lobis calycis lateralibus sub anthesi truncato- sublunaribus differt. Typus: Sri Lanka, Kanneliya, Cramer 4317 (holotypus, PDA; isotypi, E, K, NVB, US).

Herba perennis. Caules e nodis inferioribus radicantes, usque II6 m adscendentes, subquadrialati, adangulos pills retrorsis praediti, succosi. Folia ovata usque obovata, 3'5-23 x 5'5-11'5 cm, basi cuneata atque petiolo subdecurrentia, apice acuminata, obscure crenata, supra et subtus parce scaberula, nervis subtus prominentibus glandulis globosis sessilibus interpositis. Inflorescentiae paniculatae, terminales, usque Io.6

cm longae. Flores in ramis lateralibus usque 9"5

cm longis secunde dispositi. Inflorescentiae axes gemma abortiva terminati, pilis capite glanduligeris dense hispiduli. Folia floralia decidua. Calyx declinatus, late campanulatus, anthesi usque 4 mm longus, in statu fructifero 8-Io mm longus; tubus intus glaber, extra glandulis globosis sessilibus praeditus; labium superius erectum, late ovatum, usque 2 x 2-5 mm, apice in caput glandulosum productum; labium inferius usque I 5 mm longum, post anthesin labio superiore longius. Corolla usque 3.2 cm longa; tubus usque I -8 cm longus, sursum latior atque lateraliter compressus, basi tenuiter geniculatus, extra parce puberulus, pallide roseo- caeruleus; labium superius spathulatum, usque I2 x 7 mm, lineis violaceis notatum; labium inferius late ovatum, usque 12 mm longum, naviculatum, extra parce hirsutulum. Stamina in labio inferiore corollae inclusa; filamenta glabra. Discus sub anthesi anterius usque 1-6 cm porrectus. Stylus glaber; rami lineares. Nuculae anguste ellipsoideae, 2-75-3'25 X I'25-2 mm, subtrigonae, supra 3-costatae, nigrae, nitidae. (Fig. 3)

SRI LANKA. Sabaragamuwa Province: Ratnapura district: Sinharaja Forest, S.E. of Weddagala, Meyier 887 (PDA, US); Kelinkande, beside watercourse, in secondary, wet, evergreen forest, Balasubramaniam 1253 (PDA); Gongala, beside stream, in secondary, wet, evergreen forest, Waas 1383 (PDA, US). S. Province: Galle district: Habarakedde (Hiniduma), C.P. 171 (PDA); Kanneliya, beside stream, in secondary, wet, evergreen forest, Cramer 4317 (PDA, holotype; E, K, NVB, US, isotypes) & 4200 (BG, K, M, PDA, US); ibid., Balasubramaniam Io44 (PDA).

Due to the forest shade under which the plant grows, the leaves are pale green and are spread out divaricately on long petioles. The panicles are not so well developed as in C. malabaricus Benth. Flowering: June-September.




FIG. 3. Coleus kanneliyensis. A, flowering branch, X ; B, calyx, X 3; C, corolla, x iI; D, stamens & style, x 31; E, seed, x 41-




9. C. mollis Benth. in DC., Prodr. 12: 77 (1848). Type: Ceylon, Walker s.n., in Hb. Benth. (lectotype, K, chosen here). C. malabaricus Benth. var. mollis (Benth.) Hook. f., Fl. Brit. Ind. 4: 626 (1885). [C. malabaricus sensu Trimen, Handb. Fl. Ceyl. 3: 374 & (1895) pp. quoad

descr.]

io. C. elongatus Trimen in J. Bot. 27: I65 (1889), & Handb. Fl. Ceyl. 3: 375 (1895); Cramer in Kew Bull. 30: 38 (1975). Type: Ceylon, Ritigala, Trimen 6 July 1887 (holotype, PDA).

Englerastrum elongatum (Trimen) Alst. in Kew Bull. 1926: 298 (1926), & in Trim., Handb. Fl. Ceyl. Suppl. 6: 236 (193I).

I I. C. zeylanicus (Benth.) Cramer, comb. nov.

Plectranthus zeylanicus Benth., Lab. Gen. & Sp. 36 (1832), & in DC., Prodr. 12: 66 (I848). Type: Ceylon, Macrae s.n. (holotype, K).

ACKNOWLEDGEMENTS

Grateful thanks are due to the Smithsonian Institution, Washington, for the travel grant which enabled me to visit the principal herbaria of India, Europe and Great Britain; these thanks go, in particular, to Dr. F. R. Fosberg, Principal Investigator, Flora of Ceylon Project, for encouragement and help in obtaining this grant. I wish to express my sincere thanks also to the Directors of the following herbaria: the Botanical Survey of India, Coimbatore; the Central National Herbarium, Calcutta; Laboratoire de Phandrogamie, Mus6um National d'Histoire Naturelle, Paris; Rijks- herbarium, Leiden; Royal Botanic Gardens, Kew; Royal Botanic Garden, Edinburgh. In no way could I omit my sincere appreciation of the help of Dr. A. J. G. H. Kostermans (Bogor) and Mr. I. C. Hedge (Edinburgh) in going through this manuscript and making valuable criticisms. I am also very grateful to Mr. B. Mathew (Kew); it was after discussions with him that I was able to decide that the. two species described in this paper were indeed new.

For the drawings of the figures I am much indebted to Mrs. M. Goonatil- leke, University of Ceylon, Peradeniya.

REFERENCES

Bentham, G. (1832). Labiatarum Genera et Species, part I. London. Bentham, G. (1848). Labiatae in A. P. De Candolle, Prodr. 12: 55-79- Blake, S. T. (I97I). A revision of Plectranthus in Australia. Contr. Queensl.

Herb. 9: 1-I20. Blume, C. L. (1826). Bijdragen tot de Flore van Nederlandsch Indie. 14: 835- Briquet, J. (1897). Labiatae in Engl. & Prantl, Pflanzenfam. 4 (3a): 348-363. Brown, R. (I8Io). Prodromus Florae Novae-Hollandiae et Insulae Van-

Diemen. Codd, L. E. (I97I). Generic limits in Plectranthus, Coleus and allied genera.

Mitt. Bot. Miinchen. IO0: 245-252. Cramer, L. H. (I975). Englerastrum or Coleus (Labiatae) in Sri Lanka? Kew

Bull. 30: 35-38.




Keng, H. (1969). Florae Malesianae Precursores XLVIII. A revision of the Malesian Labiatae. Gard. Bull. Singapore 24: 13-I8o.

Launert, E. (1968). Miscellaneous notes on Labiatae. Mitt. Bot. Mtinchen 7: 295-307.

Loureiro, de J. (1790). Flora Cochinchinensis 2: 272. Lisbon. Morton, J. K. (1962). Cytogenetic studies on the West African Labiatae.

J. Linn. Soc. (Bot.) 58: 231-283. Mukerjee, S. K. (I940). A revision of the Labiatae of the Indian Empire.

Rec. Bot. Surv. Ind. 14(I): 1-228.



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A Revision of Coleus (Labiatae) in Sri Lanka (Ceylon)