Read a Stem Cross-Section

A young dicot stem has an epidermis, a collenchymatous hypodermis, a general cortex of thin-walled parenchyma, and an innermost starch-rich endodermis (the starch sheath). Inside it, semi-lunar sclerenchyma patches of the pericycle sit above the phloem. Vascular bundles form a ring; each is conjoint and open because cambium lies between xylem and phloem. Parenchymatous medullary rays separate bundles, and the pith occupies the centre.

A monocot stem has a sclerenchymatous hypodermis and many scattered vascular bundles in largely undifferentiated ground tissue. The bundles are conjoint and closed (no cambium), are surrounded by a sclerenchymatous bundle sheath, and lack phloem parenchyma. A water-containing cavity occurs in the bundle near the protoxylem. Peripheral bundles are generally smaller than central ones.

If xylem and phloem lie on the same radius, the bundle is conjoint. If cambium separates them, it is open and can produce secondary xylem and phloem. If cambium is absent, it is closed. In a typical dicot stem, phloem is toward the outside, xylem toward the centre, and cambium between them.

The general dicot cortex is living parenchyma. The collenchymatous hypodermis and starch-rich endodermis are also living. The semi-lunar pericycle patches above phloem are sclerenchyma and are the first dead tissue encountered inward from the stem surface. Keep each region tied to its position rather than choosing by tissue name alone.

In the linked section, the epidermis with stomata and trichomes is label ii; the starch sheath is the endodermis at v; sclerenchymatous patches above phloem form the pericycle at vi; and the central pith is xi. Read the layers from the exterior inward before matching a function.