Xylem Definition

Xylem Sentence Examples

• Differentiation of the xylem progresses outwards, of the phloem inwards, but the two tissues never meet in the centre.

• After the cambium has been active for some time producing secondary xylem and phloem, the latter consisting of sievetubes, phloem-parenchyma and frequently thick-walled fibres, a second cambium is developed in the pericycle; this produces a second vascular zone, which is in turn followed by a third cambium, and so on, until several hollow cylinders are developed.

• A leaf-trace, as it passes through the cortex, has a collateral structure, the protoxylem being situated at the inner edge of the xylem; when it reaches the leaf-base the position of the spiral tracheids is gradually altered, and the endarch arrangement (protoxylem internal) gives place to a mesarch structure (protoxylem more or less central and not on the edge of the xylem strand).

• All the metaxylems join at the nodes into a complete ring of xylem.

• New tangential walls arise in the cells which are the seat of cambial activity, and an initial layer of cells is established which cuts off tissue mother-cells on the inside and outside, alternately contributing to the xylem and to the phloem.