The cell wall has undergone secondary thickening , and is often lignified.
细胞壁多发生木质化而次生加厚.
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Fig .6 showing the secondary thickening between the gyres of the helix ( arrow ).
图6示次生壁物质在螺旋构架之间的填充 ( 箭头 ).
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Secondary vascular tissue, found only in plants with secondary thickening , develops from the vascular cambium.
次生维管组织由维管形成层发育而来, 仅存在于有次生加厚的植物中.
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