A column of specialized cells found in the phloem, specialized to conduct organic matter from sources (such as photosynthesizing leaves) to sinks (such as roots). Found principally in flowering plants.

a long tube-like structure consisting of blast cells arranged in a longitudinal row, with the cells interconnected by sieve plates.

of phloem, a continuous longitudinal tube characterised by sieve plates, non-lignified secondary cell walls and a living protoplast.