|
''Banksia ilicifolia'', commonly known as holly-leaved banksia, is a tree in the family Proteaceae. Endemic to southwest Western Australia, it belongs to ''Banksia'' subg. ''Isostylis'', a subgenus of three closely related ''Banksia'' species with inflorescences that are dome-shaped heads rather than characteristic ''Banksia'' flower spikes. It is generally a tree up to tall with a columnar or irregular habit. Both the scientific and common names arise from the similarity of its foliage to that of the English holly ''Ilex aquifolium''; the glossy green leaves generally have very prickly serrated margins, although some plants lack toothed leaves. The inflorescences are initially yellow but become red-tinged with maturity; this acts as a signal to alert birds that the flowers have opened and nectar is available. Robert Brown described ''Banksia ilicifolia'' in 1810. Although ''Banksia ilicifolia'' is variable in growth form, with low coastal shrubby forms on the south coast near Albany, there are no recognised varieties as such. Distributed broadly, the species is restricted to sandy soils. Unlike its close relatives which are killed by fire and repopulate from seed, ''Banksia ilicifolia'' regenerates after bushfire by regrowing from epicormic buds under its bark. It is rarely cultivated. ==Description== ''Banksia ilicifolia'' is a variable species. It usually grows as an erect tree up to in height, but some populations along the south coast consist of small trees or even spreading shrubs. It is generally a high small tree in the Margaret River region. The leaves arising from many short branchlets make a dense foliage close to the trunk and branches. ''Banksia ilicifolia'' has a stout trunk up to 50 cm (20 in) in diameter, and rough, fibrous, grey bark which is up to 2 cm (0.8 in) thick.〔 New growth takes place mainly in summer.〔 Young branchlets are covered in hair which they lose after two or three years. Leaves grow on stems less than two years of age, and are arranged in a scattered pattern along the stems although crowded at the apices (branchlet tips). Resembling those of holly, its leaves are a dark shiny green colour, and variously obovate (egg-shaped), elliptic, truncate or undulate (wavy) in shape, and 3–10 cm (1–4 in) long. Generally serrated, the leaf edges have up to 14 prickly "teeth" separated by broad v- to u-shaped sinuses along each side, although some leaves have margins lacking teeth. The leaves sit atop petioles 0.3–1 cm (0.1–0.4 in) in length. The upper and undersurface of the leaves are initially covered in fine hairs but become smooth with maturity. Flowering takes place from late winter to early summer. The inflorescences are dome-shaped flower heads rather than spikes as many other banksias, and arise from stems that are around a year old. No lateral branchlets grow outwards from the node where the flower head arises.〔 The flower heads measure 7–9 cm (2.8–3.6 in) in diameter, and bear 60 to 100 individual flowers. The inflorescences pass through three colour phases, being initially yellow, then pink, then finally red, before falling away from the head. One to three follicles develop from fertilised flowers, and remain embedded in the woody base of the flower head. Each follicle bears one or two seeds. The cotyledon leaves are a dull green with no visible nerves or markings. Transversely elliptic in shape, they measure 8 to 13 mm long by 12 to 18 mm wide and range from convex to concave. The pointed spreading auricles are 1.5 mm long. The cotyledon leaves sit atop the stout hypocotyl, which is green and smooth. The seedling leaves are crowded above the cotyledons. Resembling those of ''B. coccinea'', they are lined with triangular lobes or "teeth" (with a u- or v-shaped sinus) and obovate to broadly lanceolate in shape. The first set of leaves measure 1 to 2.5 cm (0.4–1 in) in length and around 1 cm (0.4 in) in width, with three or four lobes in each margin. Both upper and lower seedling leaf surfaces are covered in spreading hairs, as is the seedling stem. Juvenile leaves are obovate to truncate or mucronate with triangular lobes and measure 4 to 10 cm (1.6–4 in) long by 1.5 to 3.5 cm (0.6–1.4 in) wide. These lobes are smaller toward the petiole and apex of the leaf.〔 In the Margaret River region, ''Banksia ilicifolia'' has been confused with ''Banksia sessilis'' var. ''cordata'' as both have prickly foliage and domed flowerheads. However, the former grows on deep sand while the latter grows on grey sand over limestone ridges. The embedded follicles of ''B. ilicifolia'' compared with the loose ones of ''B. sessilis'' are another distinguishing feature.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Banksia ilicifolia」の詳細全文を読む スポンサード リンク
|