protoxylem การใช้

• The protoxylem is thus found in the central core and the metaxylem in a cylinder around it.
• Protoxylem occurred both at the tips of the lobes of the xylem strand and in the centre.
• Internal phloem is mostly primary, and begins differentiation later than the external phloem and protoxylem, though it is not without exceptions.
• The xylem development was'mesarch', i . e . the first maturing protoxylem had later maturing metaxylem on either side.
• The plant fossils found show many structural and anatomical adaptations to an aquatic environment, including a reduced vascular system, aerenchyma in tissues ( air spaces to provide buoyancy ), and protoxylem lacunae surrounded by a ring of cells with thickened inner walls.