Vascular tissue

Since the xylem and phloem function in the conduction of water, minerals, and nutrients throughout the plant, it is not surprising that their form should be similar to pipes.

The individual cells of phloem are connected end-to-end, just as the sections of a pipe might be.

These bundles include both xylem and phloem, as well as supporting and protective cells.

Because this growth ruptures the epidermis of the stem, woody plants also have a cork cambium that develops among the phloem.

This is why aphids are typically found on the undersides of the leaves rather than on the top, since the phloem transports sugars manufactured by the plant and they are closer to the lower surface.