Leucospermum

Morphology of the individual flower and leaf  the positioning of flower buds on the receptacle as seen from aboveMost pincushions are upright shrubs or even small trees of 1–5 m (3.3–16.4 ft) high, that usually have a single main stem. Some species however only have trailing branches and can form low mats, 1–5 m (3.3–16.4 ft) in diameter. Yet another set of species grow several stems directly from a rootstock in the ground. This is an important character in distinguishing between some species. Dried specimens of L. pedunculatum and L. prostratum can be difficult to distinguish, but although both are prostrate species, the growth habits in the field differ considerably. In L. pedunculatum many horizontally spreading branches develop from an about 30 cm (12 in) main stem, in L. prostratum the branches rise from an underground woody rootstock. The leaves are alternately set along the stem, distanced and slightly pointing towards the tip of the branch or overlapping, mostly without, sometimes with a leaf stalk but always without stipules at their base, 1½–14 cm (0.6–5.6 in) long and linear, elliptic, oblanceolate, oval, inverted egg-shaped or spade-shaped, the edge entire or with up to 17 teeth towards the tip, hairless or with a covering of soft cringy one-celled hairs, sometime interspersed with longer straight silky hairs.The flower heads are seated or have a short stalk, and grow individually in species with large heads or with two to ten together in species with smaller heads, in the axils of the leaves near the end of the branches. The general shape of the heads is a flattened, round, egg- or cone-shaped sphere of 2–15 cm (0.79–5.91 in) in diameter. The position not at the very tip of the branches helps to distinguish Leucospermum from related genera such as Diastella, while the more than one head per branch helps to distinguish the sections Diastelloides and Hamatum from the other sections. The involucral bracts are green in fresh specimens, and inconspicuous. They may have different shapes such as linear or ovate, with a sharp or pointed tip. In the majority of the species the involucral bracts have tough rubbery consistency and are usually softly hairy, overlapping and tightly pressed against the flower head.  L. parile, L. tottum and L. vestitum on the other hand have thin, papery bracts. The common base of the flowers that jointly constitute a single flowerhead (called receptacle) varies considerably among species. It may be flat, globe-shaped, pointy conical or blunt cylindric. This character can best be seen by cutting a flower head lengthwise in two equal halves.The individual flowers are subtended by a bract (or bracteole) that is wooly at its foot and softly hairy or hairless near the tip. Sometimes it grows on while the flower is in bloom and eventually becomes woody. While still in the bud, the perianth is a tube of 1½–5½ cm (0.6–2.2 in) long. When flowering, the perianth is yellow, orange, crimson, pink or white in color, straight or often curved towards the center of the flower head. The perianth consists of four tepals that are fused into a tube of 0.3–1.0 cm (0.12–0.39 in) either of uniform width or expanding towards the tip, but there are also a few species where it is inflated nearer the tip, such as in L. utriculosum, L. hamatum and L. harpagonatum. Above the tube, three of the lobes may become a fused in a sheath, open towards the outside of the flower head, while the lobe facing the rim of the flower head is free. In the upper part of the perianth (or limbs) all four lobes may remain fused or only the three that remained already fused in the middle part. In the section Diastelloidea all four lobes are free in the upper parts and curl back forming a four-part rim around the top of the tube. The anthers differ little between species of Leucospermum and are usually fused with the tips of the perianth lobes, and filaments cannot be identified, but in the species that constitute the section Brevifilamentum, a filament of 1–1⅛ mm (0.2–0.3 in) long makes the connection between the anther and the lobe. The buds are ripped open along a suture facing away from the center of the flower head by the style that growth in length quickly, eventually reaching a length of 1–8 cm (0.39–3.15 in), straight or with a curve towards the center of the flower head, 1–2 mm (0.039–0.079 in) in diameter, often narrower nearer to the tip or thread-shaped, mostly identically colored as the perianth. The end of the style is (sometimes only slightly) thickened and holds the pollen that is transferred there just before the bud rips open. There is a considerable morphological variation in this so-called pollen presenter between species. The pollen presenter may be cylindric, oval, or conic in shape, either or not split in two lobes near the tip or oblique. The very tip has a groove that functions as the stigma that is centrally or oblique oriented. The finely powdery ovary is 1–2 mm (0.039–0.079 in) long, and gradually merges into the style base. It consists of one carpel and contains a single pendulous ovule. At the base of the ovary are four linear or awl-shaped scales of 1–3 mm (0.039–0.118 in) long that secrete a copious amount of nectar.The indehiscent fruit consists of one cavity, containing one oval to globe-shaped seed of 4–8 mm (0.16–0.31 in) long, with a broad indent where it was attached, hairless or covered with a fine powder and generally partially covered by a pale elaiosome.The sixteen Leucospermum species that have been analysed are all diploids having twelve sets of homologue chromosomes (2n=24), which is consistent with the rest of the subtribe Proteinae.
Differences with related generaEdit
  Detail of an individual flower showing the white fruit that the genus is named after. Photo: Tony Rebelo.Leucospermum differs from genera such as Protea, Leucadendron, Mimetes, Diastella, Paranomus, Serruria, and Orothamnus by having the flower heads in the axils of the leaves (although often very near the tip of the branch), small and inconspicuous bracts subtending the head, brightly coloured styles that are straight or curve toward the center of the flower head and extend far from the perianth, giving the flower head the appearance of a pincushion, and large nut-like fruits covered by a pale and soft layer that attracts ants. The style breaks out of the bud at the side facing the rim of the head, and the perianth lobes may stick together with four or three forming a sheath, or roll back individually.SectionsEdit
Currently, the genus is subdivided in nine sections based on morphological communalities and differences.
BrevifilamentumEdit
The six species of the section Brevifilamentum are sometimes called showy pincushions, and include several horticultural species. The species all share a character that is unique in the genus Leucospermum: their anthers top a short, 1–1½ mm (0.02–0.06 in) long filament that attach the anthers to the perianth, while in all other sections the anthers are directly fused with the limbs of the perianth lobes. The common base of the flowers in one head (or involucral receptacle) as can be seen by cutting lengthwise through a head is very narrowly conical with a sharp tip. The pollen presenter is egg-shaped, obliquely egg-shaped or hoof-shaped.
CardinistyleEdit
The six species that are assigned to the section Cardinistyle are sometimes called fireworks pincushions. They are all large upright shrubs, with only one main stem. The common base of the flowers is a narrow cone with a pointy tip. The flowers have styles of 5½–8 cm (2.2–3.2 in) long that move downward when the flowers open, and are topped by a narrow pollen presenter ending in a sharp tip. L. reflexum has oval or narrowly oval greyish, felty leaves of 2–5½ cm (0.8–2.2 in) long and ½–1⅓ cm (0.2–0.55 in) wide. The perianth is yellow or scarlet 4–5 cm (1.6–2 in) long, and a style uniquely pointing downwards when the flower is open.
ConocarpodendronEdit
The three species and one subspecies of the section Conocarpodendron are sometimes called tree pincushions. They are all small trees of up to 4 m (13 ft) high with a single trunk. The common base of the flowers in the same head is conical or narrowly conical with a pointy tip. The styles are 5–6 cm (2.0–2.4 in) long that carries a narrowly conical pollen presenter with a pointy tip. The bracts that subtend the flower heads are pointed and may have a hooked tip.
CrassicaudexEdit
The four species assigned to the section Crassicaudex are sometimes called cylindric pincushions. These four all have a cylinder-shaped common base of the flowers in the same head. All are upright shrubs with several main stems that rise up from a woody rootstock underground. This makes the species very tolerant to fire. The leaves are wedge-shaped. All three species that occur outside the Cape Floral Region are assigned to this section.
CrinitaeEdit
The four species of the section Crinitae are sometimes called flat pincushions. They are upright or spreading shrubs. The involucral receptacle is always flat and 2–4 cm (0.79–1.57 in) in diameter with bowl-shaped flower heads. The lobes of the perianth remain erect after flowering and do not curl back as usual in other sections. The styles are thread-like and the flowers change color conspicuously when aging. L. saxatile is a creeper with 2–5 mm (0.079–0.197 in) wide leaves and lime-green flowers. L. gracile is also a prostrate shrub with 2–5 mm wide leaves, but its flowers are yellow. L. oleifolium has leaves 10 – 85 mm wide that are mostly entire but sometimes have up to five teeth, and with flowers that are pale yellow at first but become crimson with age. L. mundii is an upright shrub with two distinct populations, one with leaves 10 – 85 mm wide that have 7 - 17 teeth at their tip, flowers pale yellow aging to orange.
DiastelloideaEdit
The species of the section Diastelloidea are sometimes called louse pincushions. They may be upright, spreading or creeping shrubs, that usually have sharply pointed leaves without teeth at the tip. The flowerheads are small and globe-shaped, mostly with two to six together very close to the tip of the branches, 1–3 cm (0.39–1.18 in) in diameter. The involucral receptacle is never flat. The style is 1–2½ cm (0.4–1.0 in) long, topped by a club-shaped, cylindric or rounded conical pollen presenter. The colour of the flower changes when ageing, from cream to pink or from yellow to orange. All four perianth lobes curl back individually to form four small rolls surrounding the style, and these rolled lobes are said to resemble lice.
HamatumEdit
The species of the section Hamatum are sometimes called hook pincushions. Both species are trailing, mat-forming species with stiff, narrow, erect leaves and have small heads with between four and twelve flowers in one whorl. The perianth tubes are inflated towards the upper end and the styles are beset by very small teeth facing towards the base, strongly curved towards the center of the head, making the head reminiscent of a grappling hook. L. hamatum has linear leaves mostly with three teeth near the tip, a poorly developed or absent involucre, but four or five very large bracts forming a pseudo-involucre subtending the four to seven flowers per head. The perianth is hairless. L. harpagonatum has entire (narrowly) linear leaves, a well-developed involucre consisting of 25–35 bracts (subtending the flower head as a whole), eight to rarely twelve flowers per head, the perianth tubes densely wooly in the upper part.
LeucospermumEdit
The species assigned to the section Leucospermum are sometimes called sandveld pincushions. Among it are both upright, spreading and creeping shrubs, and leaf-shapes vary from line- to egg- and wedge-shaped, but they all have felty hairy leaves, even when aged. The bud is usually straight, always with a sweet scent and colored brightly yellow. In the open flower, the three perianth lobes at the side of the center of the flower head remain attached, while the remaining lobe is free. The pollen presenter at the tip of the style is cylindrical or club-shaped.
TumiditubusEdit
The species assigned to the section Tumiditubus are sometimes called wide-tubed pincushions. All eight of them are erect or spreading shrubs with one main stem. All of them have a conical or wide-conical common base of the flowers within one head. The base of lowest, fully fused part of the flower (called tube) is narrow and gets wider towards the upper end.

Leucospermum

Leucospermum

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