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''Bidens alba'', which belongs to the family Asteraceae, is most commonly known as shepherd's needles, beggarticks, Spanish needles or butterfly needles.〔''Bidens alba''. Ed. Linda C. Duever. FLORIDATA: 21 Nov. 2003. 27 May 2013.〕 ''Bidens'' means two- toothed, describing the two projections found at the top of the seeds, and ''alba'' refers to the white ray florets.〔Futch, Stephen H., and David W. Hall2. "Identification of Broadleaf Weeds in Citrus1". Gainesville: Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Science, University of Florida, 2002. N. 27 May 2013.〕 This plant is found in tropical and subtropical regions of North America, Asia, South America, and Africa,〔"Bidens alba." University of Texas At Austin. Lady Bird Johnson Wildflower Center, n.d. Native Plant. 28 May 2013.〕 situated in gardens, road sides, farm fields and disturbed sites.〔Deane, Green. "Spanish Needles, Pitchfork Weed". Eat the Weeds and other things too, 19 Oct.2011.〕 ''B. alba'' is an annual or short-lived perennial, which is considered an weed in the United States.〔 However, ''B. alba'' leaves are edible and can be used as medicinal remedies.〔 ==Description== ''Bidens alba'' is a vascular plant. It has a similar root and stem system to others in the ''Aster'' family, all of whose members are dicots.〔David W. Hall, Vernon V. Vandiver, and Jason A. Ferrell2. "Common Beggar's-tick (Hairy Beggar's-tick), Bidens alba (L.)" DC.1. University of Florida IFAS Extension, SP37 (1991):N. Web. 25 May 2013.〕 After germinating, the roots progress into a tap root that grows vertically in the ground.〔 The primary tissue of the apical meristems increases the length of the plant and the secondary roots of the lateral meristems give rise to the width. ''B. alba'' grows to a height of approximately five feet tall.〔 The stem of ''B. alba'' plant emerges from the taproot, yet the bent stem at the base also has the ability to grow into roots at the lower nodes. Stems are mostly hairless and green to purplish in color.〔 The vascular bundle provides nutrients throughout the plant, with the phloem transporting water from the roots and the xylem obtaining food from the leaves.〔 ''Bidens alba'' leaves, which are simple on the opposite side and compound on the underneath, are long and wide.〔 The underside leaf is hairy, and has toothed edges.〔 The leaves may be lobed, depending on the species. Some have teeth and some do not; each node produces two leaves along the stem.〔 Each flowering head of ''B. alba'', which is small, appears in radial symmetry.〔 The flowers on this plant are depicted as daisy-like due to the larger white petals and the very small yellow flowers which are located at the end of the branches.〔 Colors of the flower-heads of ''Bidens alba'' vary depending on the subspecies; some ''B. alba'' have yellow, tubular central blossoms and others may have flower-heads with white or cream petals ( long); eventually they form black linear seeds, yielding approximately 1200 seeds per plant.〔 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「Bidens alba」の詳細全文を読む スポンサード リンク
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