Kadua st-johnii
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Kadua st-johnii is a plant from the genus Kadua in the family of the Rubiaceae (Rubiaceae). It is endemic to Hawaii .
description
Vegetative characteristics
Kadua st-johnii grows perennial , succulent plant, the stems of which reach lengths of up to 0.3 meters. The stems, which are somewhat woody at the base, have a square cross-section and are grooved lengthways. The epidermis is cork-like .
The opposite leaves are cluster-like in the lower part of the stem. The simple, fleshy leaf blade is ovoid to broadly elliptical in shape with a length of 5.5 to 15 centimeters and a width of 2 to 7.5 centimeters wide. The top of the leaf blade is glossy dark green while the underside is more or less glaucous . The spreading edge is entire. Several pairs of network-like branching lateral nerves branch off from each side of the leaf central nerve. The approximately 0.3 to 0.35 centimeter long stipules are broadly triangular and have an approximately 0.15 centimeter long spike tip.
Generative characteristics
The narrow panicle-like inflorescences are on an approximately 7 to 15 centimeter long inflorescence stem. The inflorescences contain several single stalked flowers. The flower stalks are 0.5 to 1.8 inches long.
The four-fold flowers are radial symmetry . The flower cup becomes 0.05 to 0.08 centimeters long and has a more or less square cross-section. The sepals are fused together to form a calyx tube. The leaf-like calyx lobes are egg-shaped with a length of about 0.3 to 0.4 centimeters and a width of also about 0.3 to 0.4 centimeters wide. The fleshy, green petals are fused together like a jug. The corolla tube reaches a length of 0.5 to 0.8 centimeters and has an approximately square cross-section. The four crown lobes reach lengths of around 0.4 centimeters. The four-lobed stylus is hairy woolly at the bottom.
The capsule fruits are lens-shaped with a length of around 0.25 to 0.3 centimeters and a thickness of about 0.7 to 0.8 centimeters. The endocarp is weakly lignified. Each of the fruits contains several dark brown to almost black seeds. They are irregularly shaped and the seed coat is granular and covered with papillae .
Occurrence and endangerment
The natural range of Kadua st-johnii is on the Hawaii island of Kaua'i .
Kadua st-johnii thrives at altitudes of 3 to 60 meters. The species grows in the crevices of coastal cliffs. At these locations the species grows together with Artemisia australis , Bidens forbesii , Capparis sandwichiana , Lipochaeta connata , Nototrichium sandwicense and Schiedea apokremnos .
Kadua st-johnii is classified as Critically Endangered on the IUCN Red List . Displacement by invasive species as well as habitat destruction by imported and feral animals as well as fires, droughts and landslides are named as the main endangerment factors. The total population, which comprises five subpopulations consisting of a total of around 45 plants , is viewed as declining.
Taxonomy
The first description as Hedyotis st-johnii was in 1958 by Benjamin Clemens Stone and Irwin E. Lane in Pacific Science . In 2005 Warren L. Wagner and David H. Lorence transferred the species as Kadua st-johnii in Systematic Botany to the genus Kadua .
Individual evidence
- ↑ a b c d e f Kadua st-johnii. In: Flora of the Hawaiian Islands. www.botany.si.edu/pacificislandbiodiversity/hawaiianflora, accessed on February 15, 2017 (English).
- ↑ a b Kadua st-johnii in the endangered Red List species the IUCN 2016 Posted by: K. Wood, JC Watson & DH Lorence, 2015. Retrieved on February 15 2017th
- ^ Kadua st-johnii at Tropicos.org. Missouri Botanical Garden, St. Louis, accessed February 15, 2017.
