Dicot stem

Epidermis: the outer protective layer, with a thin cuticle; it may carry trichomes and a few stomata.

Cortex lies between epidermis and pericycle and has three sub-zones: hypodermis, general cortex and endodermis.

Hypodermis: a few layers of collenchyma just under the epidermis, giving the young stem mechanical strength.

Below it, rounded thin-walled parenchyma cells with clear intercellular spaces.

Endodermis: the innermost cortex layer. Its cells are full of starch grains, so it is also called the starch sheath.

Pericycle: semi-lunar patches of sclerenchyma sitting just above the phloem, inside the endodermis.

Vascular bundles are many and arranged in a ring, the mark of a dicot stem. Each is conjoint and open, with endarch protoxylem (protoxylem towards the centre).

Medullary rays: a few layers of radially placed parenchyma between neighbouring bundles.

Pith: the central region of many rounded parenchyma cells with large intercellular spaces.