Phenology. Flowers and fruits mainly from October to May of the following year. Due to irregular regional rainfall, plants tend to flower sporadically during this period in response to significant rainfall events.

Distribution & habitat. Hemigenia glaucissima is currently known from two sites geographically associated with the Parker Range, south-east of Southern Cross, Western Australia (Figure 2). Plants occur in mallee eucalypt woodland, associated with yellow sands and with surface laterite.

Conservation status. Likely to be localised and rare as it is currently only known only from two sites; neither site is within areas reserved for conservation. Hemigenia glaucissima should be listed as a conservation priority taxon in Western Australia.

Etymology. The botanical name is derived from the Latin ‘glaucus’ (bluish-green or grey) and the adjectival superlative ‘–issimus’ (very), in reference to the conspicuously glaucous surfaces of the leaves, branchlets, bracteoles and calyces, which give this species its distinctive appearance (Figure 1).

Vernacular name. Parker Range Hemigenia.

Notes. The glabrous and glaucous surfaces (along with the bluish green to greyish purple colouration) of the leaves, young stems, pedicels, bracteoles, and calyces of Hemigenia glaucissima, makes this species distinctive within the genus. This species shares some morphological similarities with the rare, northern Wheatbelt species H. diadela. Both species have greyish green leaves that are arranged in whorls of 3, inconspicuous petioles and small tufts of hairs in the leaf axils, zygomorphic flowers with lilac, 2-lipped corollas and mericarps with glandular hairs at their apex. Hemigenia diadela can be differentiated from H. glaucissima by having lanceolate leaves with hairs along the basal margins (versus leaves mostly ovate to obovate and glabrous in H. glaucissima); stems and pedicels with a dense indumentum of short hairs combined with longer, more sparsely distributed hairs (vs glabrous stems and pedicels); sparse indumentum of multicellular hairs on the bracteoles and calyces (vs glabrous bracteoles and calyces); and strongly zygomorphic calyces (vs nearly radially symmetric calyces, with 5 acute calyx lobes of similar length).

There are also some morphological similarities between H. glaucissima and H. humilis s.l. in terms of the leaf shape, size and orientation along stems. Additionally, both species have shortly pedicellate flowers and calyces with 5 acute lobes of similar length. Hemigenia humilis is a variable species consisting of several informal, morphological variants. Most variants of H. humilis (including the type variant [K000975382 image!]) are variously hairy on the stems, leaves, calyces and can be easily distinguished from H. glaucissima. However, an ‘inland variant’ of H. humilis (distributed around Narrogin [PERTH 03671402, PERTH 05562821], Arthur River [PERTH 06238475] and Nyabing [PERTH 03671399]) is the most visually akin to H. glaucissima in that it has glabrous and glaucescent stems, leaves and calyces. All variants of H. humilis can readily be distinguished from H. glaucissima as they all have opposite and decussately arranged leaves (vs leaves in whorls of 3 in H. glaucissima), floral bracteoles distinctly subterminal (1/3 to 2/3) along pedicels (vs terminal at the base of the calyx), hairy outer corolla surfaces (vs glabrous outer corolla surfaces) and mericarps that are elongate and glabrous (vs cerebriform with a dense covering of trichomes at the apex).

Open-access, online, rapid taxonomy ISSN: 2653-4649 (Online)

Australian Journal of

Taxonomy

Open-access, online, rapid taxonomy
ISSN: 2653-4649 (Online)