Trichodesma stocksii Boissier (1856: 140)

Thulin, Mats & Larsson, Anders, 2021, New country records for species of Boraginaceae and Lamiaceae in the Horn of Africa hotspot, Phytotaxa 513 (1), pp. 62-68 : 64-66

Trichodesma stocksii Boissier (1856: 140)

Synonym:— Trichodesma longipedicellatum Rech. f. & Riedl in Riedl (1967: 222).

New specimen records:— YEMEN. Hadramaut: 20 km from As Sufal on road along Wadi Hajr , elev. 150 m, 21 November 1998, flowering and fruiting, Thulin, Beier & Mohammed A. Hussein 9923 ( E!, K!, UPS!); Middle Wadi Hajar , c. 15 km NW of Meyfah, elev. 150 m, 15 November 1999, flowering and fruiting, Hein 6395 ( B [digital image!], E!) .

This is a new record for Yemen ( Fig. 3). The two collections cited were both made on stony barren hillsides on black volcanic rocks. The vegetation in the surrounding area is sparse, but included several rare species, such as Tephrosia hadramautica Thulin (1994: 487) , Indigofera rubromarginata Thulin (1996: 519) , and Ochradenus spartioides ( Schwartz 1939: 76) Abdallah (1967: 67) . Tephrosia hadramautica and O. spartioides are endemic to southern Yemen, whereas I. rubromarginata is also found in Oman. A drawing based on the collection Thulin et al. 9923 is shown in Fig. 4 .

Two further specimens from Yemen have been seen that may represent Trichodesma stocksii , but are too young to be identified with certainty:

YEMEN. Lahij: Juhali Hills, 60 miles NW of Aden, elev. 600–1200 m, May 1904, flowering, Wahab s.n. ( E!) ; Hadramaut: Mukalla to Moula Matar , elev. 300 m, 19 March 1964, flowering, Rauh & Lavranos 13305 ( K!) .

Trichodesma stocksii was described from “regione Beloutschistan” ( Pakistan) based on a collection made by Stocks ( Boissier 1856). Due to its nutlets with membranaceous and strongly inflexed margins, it was placed in T. sect. Ommatocaryum De Candolle (1846: 174). Boissier (1879) also cited material from Iran, as well as Aucher-Eloy 5025 from “regno Mascate Arabiae” in todayʼs Oman. Since then more collections have been made in Iran, Pakistan, and Oman, and the species was keyed out in a “Key to the Trichodesma species recorded from the Arabian peninsula” provided by Mosti & Selvi (2007). The species was not accounted for in Flora of the Sultanate of Oman ( Ghazanfar 2015), but some collections from Oman were listed by Patzelt et al. (2020).

Trichodesma longipedicellatum , based on a collection from Pakistan (Rechinger & Riedl in Riedl 1967), was said to appear to be “only a tall form of T. stocksii , growing under better conditions” by Kazmi (1971). Subsequently, Nasir (1989) treated T. longipedicellatum as a synonym of T. stocksii , and the specimens treated as T. longipedicellatum in Iran by Mozaffarian (1985) were regarded as falling within the variation of T. stocksii by Khatamsaz (2002).

The two collections from Yemen cited above, apart from having nutlets with strongly inflexed and almost wheelshaped margins ( Fig. 4H ), both have relatively large and broad leaves, some of which are distinctly petiolate ( Fig. 4B ). They resemble the type of T. longipedicellatum rather than the majority of specimens from Iran and Oman that tend to have narrower and almost sessile leaves, often with somewhat reflexed margins. A map of the total distribution of T. stocksii is provided in Fig. 3.

Figures

FIGURE 4. Trichodesma stocksii. A. Portion of plant with flowers and young fruits. B. Basal leaf. C. Flower. D. Calyx at anthesis. E. Corolla tube opened up to show stamens. F. Pistil. G. Fruiting calyx flattened out to show ovary with two undeveloped nutlets and with two nutlets detached. H. Two mature nutlets and two undeveloped nutlets at base of style. I. Nutlet from below showing attachment area. J. Seed. Scales 20 mm (A, B), 5 mm (C, G, H), 2 mm (D, I), and 1 mm (E, F, J). All from Thulin et al. 9923. Drawn by Margaret Tebbs.