One of the tubular conductive structures of xylem,consisting of dead cylindrical cells that are attached end to end and connected by perforations. They are found in nearly all flowering plants.

• 管束本质部的一种导管结构，包含死掉的圆管状细胞，它们一个连着一个，由孔联接起来，几乎在所有开花植物中都能找到它们