The genera of Leguminosae-Caesalpinioideae & Swartzieae
Type species: H. unifoliolatum Cowan.
Habit and leaf form. Small trees (to 10 m), or shrubs; unarmed.
The leaves ostensibly simple (unifoliolate); pinnately veined, with a predominant midrib. Stipules usually present, persistent and conspicuous in mature leaves (but sometimes deciduous, to 1.5 mm long); membranous; not connate.
Inflorescence and floral morphology. The inflorescences axillary; unbranched; simple racemes. Bracts persistent beyond anthesis. Bracteoles present; small, not enclosing the flower buds; persistent beyond anthesis; not valvate; free.
The flowers fragrant; hermaphrodite; not papilionaceous; not pentamerous throughout; departing from pentamery in the calyx; white or green (white). Hypanthium absent, the androecium hypogynous. Calyx 3–4 (the segments reflexed after anthesis); covering the rest of the flower in bud; Swartzieae type (closed before flowering, splitting more or less irregularly into valvate lobes or teeth); gamosepalous; markedly irregular; members not imbricate. Corolla present; regular; 5; without greatly reduced members; polypetalous. Petals all sessile (all more or ess similar in size, broadly ovate); imbricate; imbricate-descending with the posterior petal (vexillum) outside; white. The androecium comprising 10 members; members all free of one another; members all more or less equal in length (being only slightly shorter and longer alternately); comprising only fertile stamens. Fertile stamens 10 (the anthers narrowly lanceolate, acuminate, laterally densely long-tomentose, and cohering by the intertwined hairs). Anthers attached at the base of the connective (dorsifixed near the base, not versatile); dehiscing longitudinally. Ovary hairy, sessile or subsessile; free. Stigma punctiform, not dilated. Ovules numerous (10–15).
Fruit, seed and seedling. Fruit a two-valved pod (with two seeds); fleshy, not becoming woody. Seeds with an inflexed radicle.
Transverse section of lamina. Leaves without conspicuous phloem transfer cells in the minor veins. Druses absent from the mesophyll (but with large prismatic crystals). Mesophyll secretory cavities absent. Adaxial hypodermis absent. Leaf girders absent. Laminae dorsiventral. Mesophyll without unaligned fibres or sclereids. Minor veins mainly with abundant accompanying fibres.
Leaf lamina epidermes. Epidermal crystals not seen either adaxially or abaxially. Simple unbranched hairs not seen. No compound or branched eglandular hairs seen. Capitate glands not seen. Hooked hairs not seen. Cassieae-type leaf pseudo-glands not seen. Expanded and embedded hair-feet absent. Basally bent hairs absent. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; not conspicuously pitted. Stomata adaxially very rare. Abaxial: Abaxial stomata not predominantly paracytic (mixed paracytics, incomplete paracytics, actinocytics and anomocytics). Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating; not conspicuously pitted in optical section; staining normally with safranin.
Wood anatomy. Wood without septate fibres; storied; without normal intercellular canals; without traumatic canals. Intervascular pits medium to large (average 5.2 microns).
Pollen ultrastructure. Tectum papillate; reticulate papillate. Length of colpi greater than one half pole to pole distance.
Cytology. Basic chromosome number, x = 10.
Species number and distribution. 1 species (H. unifoliatum). Eastern Brazil.
Tribe. Papilionoideae-Exostyleae (former Swartzieae).
Miscellaneous. Illustrations: • H. unifoliolatum: R.S. Cowan. • H. unifoliolatum: leaf anatomy, fruit and seeds.
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classification. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1993 onwards. The genera of Leguminosae-Caesalpinioideae and Swartzieae: descriptions, illustrations, identification, and information retrieval. In English and French. Version: 22nd March 2017. delta-intkey.com/caes’.