Enigmatic morphology ofDjinga felicis(Podostemaceae - Podostemoideae), a badly known endemic from northwestern Cameroon

Abstract

Djinga is a monotypic genus restricted to the Cameroon Ridge (‘Dorsale Camerounaise’) of NW Cameroon. Besides the type locality Mount Djinga (Adamawa Province, near Tignère), it also grows in waterfalls near Mount Oku (NW Province). This paper describes the structure and development of Djinga felicis using scanning electron microscopy and microtome sections. Cusset's protologue is enriched considerably. Roots are green, dorsiventrally flattened and adherent to submerged rocks. They are broad ribbons or crusts (up to 1 cm broad) which branch exogenously. Root‐borne shoots (up to 17 cm) have filamentous leaves with sheaths and (occasionally) attached stipules. Flowers are borne as part of reproductive short shoots which arise exogenously along the stems and endogenously along the roots. Djinga shows non‐axillary stem branching. Reproductive shoots along the main stem usually stay short. They arise from the abaxial side of double‐sheathed leaves, a key innovation of Podostemoideae. These short shoots shift into pocket‐like stem positions clearly below their associated leaves. Each flower bud inside a spathella is erect, but with an inclined ovary. The flowers are unistaminate with a broad connective. Unlike many other Podostemoideae, the tricolpate pollen grains are arranged in both dyads and monads. The ovary is globular and unilocular. The mature 8‐ribbed capsule dehisces by two slightly unequal valves, releasing 40–50 seeds. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160, 64–81.

DNA barcoding of African Podostemaceae (river‐weeds): A test of proposed barcode regions

“…Most currently recognised species have extremely limited distributions (e.g., occurring in a single river or set of waterfalls), and there is a high level of endemism (Cook & Rutishauser, 2007). There is limited knowledge of the African taxa in particular (although recent progress has been made in our understanding of some species, e.g., Ghogue & al., 2009), and species may lack clear diagnostic characters (Moline & al., 2007). It has been suggested that the large number of endemic taxa within the family could be a taxonomic artefact, resulting from insufficient knowledge of many species (Cook & Rutishauser, 2007;Moline & al., 2007).…”

Djinga cheekii sp. nov. (Podostemaceae) from Cameroon

“…Djinga cheekii sp. nov. looks similar to D. felicis , as described in detail by Ghogue et al (2009). However, it has always two stamens (n = 50 flowers) whereas D. felicis has only one stamen per flower.…”

“…Djinga cheekii as well as L. linearifolia and L. pusilla have firm dyads throughout, whereas in D. felicis the pollen are arranged in dyads which start to decay into monads during anthesis. Ghogue et al (2009) found ca 80% dyads and ca 20% monads in nearly mature anthers of D. felicis . Unlike typical D. felicis (having elongated stems), there are only rosette‐like shootlets up to 6 mm in D. cheekii , arising endogenously from crustose roots.…”

“…The main characters shared by the four species are: rooting structures (‘roots’) as dorsiventral crusts with exogenous lobes; leaves with narrow bases, arranged in one plane; pollen shed in dyads; capsules slightly anisolobous, 3 ribs per valve, two linear stigma lobes. The majority of African Podostemoideae (including Djinga and Ledermanniella ) have uni‐locular ovaries whereas nearly all American and Australasian podostemoids have bi‐locular ovaries (Rutishauser et al 2004, Ghogue et al 2009).…”

“…Ghogue, however, found D. felicis again at five other places along the Adamawa ridge: 250 km southwest of Mount Djinga in a small area of about 50 km in diameter in the Bamenda highlands: Fundong, Anyanjua, Sabga, Bambili and Fembvang junction on the road Bambui – Belo [GHO2090]. The peculiar morphology of D. felicis was analyzed by Ghogue et al (2009). As part of two collection trips of the first author (Ghogue) during 2004 and 2011 a new taxon was discovered in the Littoral Province, resembling D. felicis but showing 2 stamens per flower (not just 1 as in D. felicis ) and having strongly inclined flower buds inside the spathella (not slightly oblique ones as in D. felicis ).…”