Hyphaene dichotoma (J.White Dubl. ex Nimmo) Furtado
Palms Southern Asia 112 (2009). -Icon.: Palms Southern Asia plate 34 (2009).
Synonyms: Borassus dichotomus J. White ex Nimmo.; Hyphaene indica Becc.; H. taprobanica Furtado
A lectotype (Fig. 1) and an epitype (Fig. 2) were recently proposed by Lawand et al. (2018) for this species.
Individuals of 15-20 m tall x 25-30 cm in diameter, suckering at the base, the stems covered with old leaf sheaths up to 5 m height in the stem (Figs. 3-4). The stems displaying 2-3 times dichotomy (2 observed in female clumps and 3 observed in male clumps), the “Schoute’s model” clearly expressed here, as almost always 90 degrees between successive branching.
Leaves per crown 14-15 (observed in male individuals), or 25-30 (female individuals), green-olive; leaf sheaths 40 cm long, with a well-developed longitudinal middle cleft; petioles strongly armed, 80 cm long and 5 cm wide at the base, 3 cm wide at the apex, abaxially convex, adaxially flat to slightly channeled, in the margins covered with grey spines, the latter about 1,5 long and 1,5 cm at the base, most of them oriented towards the apex and inserted every 3-4 cm; costa not seen, hastula asymmetrical, 4 cm long; leaf segments 56 per blade.
Male inflorescence with a cartaceous, 40 cm long prophyll, the latter externally striate and smooth internally; peduncular bracts 1-2, 30-40 cm long, similar to prophyll; rachillae 7-13, spirally inserted; rachis 1.2 m long, completely covered by the rachillae bracts, the latter up to 40 cm long; basal rachillae with a sterile portion 22 x 1.2 cm, topped by 2 rachillae of 22 x 1.2 cm; mid-length rachillae with a sterile portion of 35 x 1.9 cm, topped by 4-5 fertile rachillae, the latter 26 x 1 cm; apical rachillae with a sterile portion of 24 x 1 cm, topped by two fertile rachillae or spicate, each rachilla 20 x 1 cm, apicalmost rachilla extending from the rachis with a fertile portion of 20 cm.
Female inflorescence with at least 2 peduncular bracts, cartaceous, each 15- 30 cm long, with an elongated and pointed apex, covered with a brownish, irregularly scattered indumentum; rachis 1 m long x 1 cm wide, elliptic in cross section, ending in a fertile rachilla 35 cm long and 1.3 cm in diameter; rachillae 5 , each subtended by one rachilla bract up to 30 cm long, the latter covered with the same indumentum as the peduncular bracts; the rachillae inserted in a spirally pattern; basal rachillae spicate with a sterile part of 35 x 1.2 cm, fertile part 35 cm x 1.3 cm; middle rachillae with a sterile part topped by 3 fertile rachillae, sterile part 22-30 x 0.8-1.4 cm, fertile part 36 x 1 cm; towards the apex of the rachis spicated or forked rachillae, sterile part 25 x 1 cm, fertile part 36 x 1 cm.
Fruits more or less oblong-globose, smooth or irregularly warted, dull brown, 4.5 long x 4 cm wide (Figs. 5, 6).
Taxonomic notes: the species Hyphaene taprobanica Furtado was long time regarded as a separate species from Hyphaene dichotoma (J.White Dubl. ex Nimmo) Furtado. The type specimen of the former (M. Tisseras) is deposited at K and according to the label of the specimen it was collected in May 1969 from one plant in the Peradeniya Botanic Garden (Sri Lanka), where only one individual was growing. The type specimen is based on two entire fruits and one fruit longitudinally divided. These fruits are very polymorphic, from ovate to oblong and measuring 6-7 cm x 4-5 cm; the seeds are 4 x 3 cm. The morphology and the dimensions of the fruits of Hyphaene taprobanica may be included in the range of variability observed in Hyphaene dichotoma.
Notes on the conservation status of H. dichotoma: The conservation status of this species was assessed by Johnson (1998) and proposed as Near Threatened (NT). More details are available at http://www.iucnredlist.org/details/38583/0. However, according to personal communication of Dr. Sreekumar (Kerala Forest Research Institute, India) the Indian doum palm Hyphaene dichotoma (White ex Dubl.) Furtado, is a threatened palm growing along the seasonal water-courses, coastal sand dunes and flat areas of Gujarat, Goa and Maharashtra, along with the union territories of Daman, Diu and Dadra (Fig. 7). An IUCN (2014) conservation assessment enlisted this species as Lower Risk/near threatened vers. 2.3, and major identified threats were among others the increasing settlement and development activities for the survival of this palm.
Fig. 1. Lectotype of Hyphaene dichotoma (J. White Dubl. ex Nimmo) Furtado (image at the left). Illustration first proposed in the publication of Bowler (1833 - see chapter of Literature for complete reference). Lectotype proposed by Lawand et al. (2018). Image kindly provided by Dr. Pramod Lawand (Department of Botany, The New College, Kolhapur, Maharashtra, India).
Fig. 2. Epitype of Hyphaene dichotoma (J. White Dubl. ex Nimmo) Furtado. Specimen P.R. Lawand PRL 001, SUK, proposed by Lawand et al. (2018). Image kindly provided by Dr. Pramod Lawand (Department of Botany, The New College, Kolhapur, Maharashtra, India).
Fig. 3. Growth habit of Hyphaene dichotoma in India (Photo Dr. Sreekumar, V.B., Kerala Forest Research Institute, India)
Fig. 4. Several male and female clumps of Hyphaene dichotoma are cultivated in the Fairchild Tropical Botanical Garden (Miami, USA) . We described this palm on site and sampled several clumps for the DNA analyses.
Fig. 5. Infructescence of Hyphaene dichotoma in India (Photo Dr. Sreekumar, V.B., Kerala Forest Research Institute, India)
Fig. 6. Fruits of Hyphaene dichotoma in India (Photo Dr. Sreekumar, V.B., Kerala Forest Research Institute, India)
Fig. 7. Distribution map (red dots) of Hyphaene dichotoma in India (Photo Dr. Sreekumar, V.B., Kerala Forest Research Institute, India)