In gymnosperms, the axial phloem consists of sieve cells and parenchyma cells, some of which become albuminous cells (see Fig. 5.5); some gymno-sperms have fibres in the phloem as well. The homocellular rays are nor-mally uniseriate. There is often very little wall thickening but sclerification can take place. The outermost phloem layers either become compacted, or are incorporated into the ‘bark’ or rhytidome.