Convolvulus prostratus Forssk., Fl. Aegypt.-Arab. 203. 1775. ( Forsskal 1775: 203).

Wood, John R. I., Williams, Bethany R. M., Mitchell, Thomas C., Carine, Mark A., Harris, David J. & Scotland, Robert W., 2015, A foundation monograph of Convolvulus L. (Convolvulaceae), PhytoKeys 51, pp. 1-282 : 135-136

111. Convolvulus prostratus Forssk., Fl. Aegypt.-Arab. 203. 1775. ( Forsskal 1775: 203). Figure 15, t. 26-34.

Ipomoea microphylla Roth ex Schult., Syst. Veg., ed. 15 bis [Roemer & Schultes] 4: 248. 1819. ( Roemer and Schultes 1819: 248). Type. INDIA, Heyne s.n. (B†).

Convolvulus parvifolius Spreng., Syst. Veg. [Sprengel] 1: 611. 1824. ( Sprengel 1824: 611). Type. Based on Ipomoea microphylla Roth ex Schult.

Convolvulus microphyllus Sieber ex Spreng., Syst. Veg. [Sprengel] 1: 611. 1824. ( Sprengel 1824: 611). Type. EGYPT, Sieber s.n. (holotype LE; isotypes E!, K!, L).

Evolvulus pilosus Roxb., Fl. Ind. (Carey & Wallich ed.) 2: 106. 1832. ( Roxburgh 1832: 106). Type. INDIA, plant cultivated in Calcutta Botanic Garden (whereabouts unknown).

Convolvulus pluricaulis Wall. ex Choisy, Mém. Soc. Phys. Genève 6: 477. 1834. ( Choisy 1834: 477). Type. INDIA, "montes Hindostania meridionalis 1825", Wallich 1316 (lectotype G 00135972!, sheet annotated " Convolvulus pluricaulis Ch.", designated here).

Convolvulus evolvuloides Boiss., Diagn. Pl. Orient. 7: 25. 1846, nom. illeg., non Convolvulus evolvuloides Desf. (1798). ( Boissier 1846: 25) Type. IRAN, Makran, Aucher-Eloy 4953 (holotype G; isotypes K!, BM!).

Convolvulus scindicus Boiss., Diagn. Pl. Orient., ser. 2, 3: 123. 1856, nom. illeg., non Convolvulus scindicus Stocks (1852). ( Boissier 1856: 123). Type. PAKISTAN, Sind, Stocks (holotype?G, possible isotypes K!).

Convolvulus microphyllus var. boissieri C.B.Clarke, Fl. Brit. India [J.D. Hooker] 4: 218. 1883. ( Clarke 1883: 218). Type. Based on Convolvulus scindicus Boiss.

Convolvulus prostratus var. boissieri (C.B.Clarke) Parmar, J. Econ. Taxon. Bot. 18: 251.1994. ( Parmar 1994: 251). Type. Based on Convolvulus scindicus Boiss.

Convolvulus pluricaulis var. macra C.B.Clarke, Fl. Brit. India [J.D. Hooker] 4: 218. 1883. ( Clarke 1883: 218). Type. INDIA, Falconer s.n. (lectotype K, sheet labelled " Evolvulus alsinoides var." and annoted Convolvulus pluricaulis var. macra " in Clarke’s handwriting, designated here).

Convolvulus deserti Hochst. & Steud. ex Baker & Rendle, Fl. Trop. Africa (Oliver et al.) 5(2): 92. 1905. ( Baker and Rendle 1905: 92). Type. SAUDI ARABIA, Jeddah, Schimper 783 (syntypes BM 000049019!, GOET, HAL, HBG, K!, L, OXF!, P!, STU, W!).

Convolvulus microphyllus var. longipes Maire, Bull. Mus. Natl. Hist. Nat. 22: 535. 1931. ( Maire 1931b: 535). Type. Central Sahara (ALGERIA?), Mauod 312 (holotype AL?; isotype P00417710!).

Convolvulus heterotrichus Maire, Bull. Soc. Hist. Nat. Afrique N. 26: 159.1935. ( Maire 1935: 159). Type. Western Sahara, Lutherear s.n. (holotype?AL; isotypes MPU006233!, P00434263!).

Convovulus microphyllus var. heterotrichus (Maire) Maire, Bull. Soc. Hist. Nat. Afrique N. 27: 251. 1936. ( Maire 1936: 251). Type. Based on Convolvulus heterotrichus Maire

Convolvulus austroaegyptiacus Abdallah & Sa’ad, Acta Bot. Neerl. 15: 190. 1966. ( Abdallah and Sa’ad 1966: 190). Type. EGYPT, Abdallah s.n. (holotype U; isotypes CAI, CAIM, K!, WAG).

Convolvulus cancerianus Abdallah & Sa’ad in Sa’ad, Meded. Bot. Mus. Herb. Rijks Univ. Utrecht 281: 176. 1967. ( Sa’ad 1967: 176). Type. EGYPT, Abdallah 1646 (holotype U; isotype CAIM, WAG).

Convolvulus microphyllus var. macra (C.B.Clarke) S.K.Sharma & Tiagi, Fl. N. E. Rajasthan 262 ( Sharma and Tiagi 1979: 262). Type. Based on Convolvulus pluricaulis var. macra C.B.Clarke

Convolvulus prostratus var. deserti (Hochst. & Steud. ex Baker & Rendle) Parmar, J. Econ. Taxon. Bot. 18: 251. 1994. ( Parmar 1994: 251). Type. Based on Convolvulus deserti Hochst. & Steud.

Convolvulus austroaegytiacus var. cancerianus (Abdallah & Sa’ad) Alfarhan, Fl. Kingdom Saudi Arabia 2(2): 166. 2001. (Alfarhan 2001: 166). Type. Based on Convolvulus cancerianus Abdallah & Sa’ad

Type.

YEMEN, Mor, Forrskål s.n. (lectotype C, designated by Sa’ad 1967: 192).

Description.

Very variable perennial herb with ascending or prostrate stems up to 70 cm long, vegetative parts thinly to densely pubescent or villous, stems often somewhat rigid and woody when old. Leaves subsessile, 0.8-3 × 0.2-0.6 cm, oblong, linear, lanceolate, narrowly lanceolate or oblanceolate, acute or obtuse, margin entire, cuneate, the lowermost tapered at the base. Flowers 1-3 (-11) in sessile or pedunculate bracteate clusters, these occasionally rather lax with individual flowers clearly separate; bracts leaf-like, exceeding, equalling or shorter than the flowers; peduncles 0-5 (-10) cm long; bracteoles 3-7 × 1-2 mm, filiform, linear to lanceolate or narrowly oblong, sometimes caducous; pedicels 0-3 (-6) mm long; outer sepals 4-8 × 1.5-6 mm, lanceolate to ovate, acuminate, green in the upper half, paler in the lower half; inner sepals caudate; corolla (6-)10-15 mm long, white or pale pink, unlobed, midpetaline bands pilose; ovary glabrous; style glabrous, divided 3-4 mm above the base, stigmas c. 4 mm. Capsule glabrous, seeds smooth, pubescent. [ Sa’ad 1967: 192; Nowroozi 2002: 105 (map); Collenette 1999: 230 photo); Austin and Ghazanfar 1979: 23, 21 (plate); Jongbloed 2003: 314 (photo)]

Distribution.

A characteristic Saharo-Sindian species, apparently absent from Palestine/Israel, Syria, most of Iraq and countries north of Iran: Cape Verde Islands ( Lobin 1986: 155); Senegal (Raynall 5778); Mauritania (Monod 18317, Adam 19415-2); Niger (Popov 41, Monod 13855); Chad; Algeria (Monod 312); Sudan (Kotschy 354, Schweinfurth 2149); Libya (fide Greuter et al. 1986); Egypt (Letourneaux 2802, Schweinfurth 138); Djibouti (Mosnier 718); Somalia (Thulin & Warfa 5800); Saudi Arabia (Trott 1458, Zohrab 107, Collenette 2418, 7887); Qatar (Mandaville 4109); Oman (Lawton 2052, Mandaville 7329); UAE (Borosova et al. 107); Yemen (Deflers 34, Lunt 158); Iraq (Rechinger 9353); Iran (Furlonge 15, Aucher-Eloy 1234); Afghanistan (Griffith 681); Pakistan (Lace 3397, Popov 63/413); India (Popov 63/380).

Notes.

Convolvulus prostratus is easily confused with Convolvulus pilosellifolius particularly in the Arabian peninsular. It is best distinguished by the lanceolate to ovate outer sepals which taper to an acuminate apex. In contrast, in Convolvulus pilosellifolius the outer sepals are oblong-oblanceolate, widest above the middle, and merely acute. Records of Convolvulus pilosellifolius from Yemen and much of the Persian/Arabian Gulf are probably errors for Convolvulus prostratus .

Convolvulus prostratus is a polymorphic species and the extremes can look very different. Variation is particularly complex in the Arabian peninsula. At least some of the variation is explained by response to rainfall ( Wood 1997: 233-234) but some of it is geographically related. The following are among the more distinct forms but it should be emphasised that all kinds of intermediates occur.

In the types of Convolvulus prostratus and Convolvulus microphyllus the flower clusters are compact, 1-3-flowered, subsessile or at most shortly pedunculate. The flower clusters appear lanceolate in form and relatively small. This is the common form in Africa, where other forms are rare or absent. Similar forms occur across Arabia to India.

In India, Pakistan and Afghanistan plants similar to (i) occur commonly but a second form corresponding to the type of Convolvulus pluricaulis is also frequent. This differs in the presence of prominent, narrowly oblong to oblanceolate bracts reaching to the apex of the stem thus resembling a perennial form of Convolvulus rottlerianus . These forms are virtually restricted to the Indian subcontinent but occur very rarely elsewhere, such as Heudelot 403 from Senegal. Examples include Haines 3412, Thomson 72, Clarke 28110 and Mooney 2025 from India, Duthie 7177, Stewart 7037, Drummond 14701 and Popov 63/413 from Pakistan and Griffith 681 from Afghanistan.

In Arabia and rather rarely elsewhere there occur plants which accord with the types of Convolvulus austroaegyptiacus and Convolvulus cancerianus . These are usually vigorous plants with stout, somewhat woody stems, the hairs spreading on the leaves and stems and the inflorescence rather lax so individual flowers are visible as in Convolvulus pilosellifolius . In some examples the flowers are very numerous, up to at least 10. Examples include Collenette 909 and Chaudhary 6696 from Saudi Arabia, Willcox 216, Lumley 50 and Borosova et al. 138 from U.A.E., Lawton 2390 from Oman and Wood 3427 and Thulin et al. 8303 from Yemen. These forms are rare elsewhere but occur in Egypt and Iran (Wright & Bent 503-103).

Occasional plants with spinescent branches occur. These appear to be restricted to Arabia and include Boulos 10931 from Qatar and Collenette 4143 from Saudi Arabia.

Plants with very woody stems which could be treated as shrubs occur occasionally, particularly in Oman. Good examples are Miller & Whitcombe 2031 & 2049 from Oman, but Collenette 9077 & 9150 from Saudi Arabia and York & El-Keblawy 55 from UAE are also distinctly woody.

Dwarf forms with very small leaves occur on Bahrain (Naguib 72, Fernandez 373, Good 196, Cornes 304) and Farasan Island in the Red Sea (Collenette 8993). These may be the result of arid conditions or salt spray and may constitute an ecotype similar to var. pumilus of Convolvulus oleifolius .

There is much variation in the number of flowers in each cluster but occasional plants occur where the flowers are solitary. Examples include Schweinfurth 2150 from Egypt, Trott 225 from Saudi Arabia and Borosova 107 from U.A.E.

No attempt has been made here to give formal names to any of this variation but it is very clear that the Convolvulus prostratus complex merits much more detailed study.