Stem of moonseed

Forms multiple layers of cambia

Slow increase in girth

Cross-section of moonseed (Menispermum sp.) stem. This plant is a vine. With the growth of the stem, multiple vascular cambia will be formed progressively outward, each to produce new secondary phloem and secondary xylem. Thus, this is an example of a stem with anomalous secondary growth.

The outer surface of the stem shows the presence of a couple of lenticels where the periderm is broken. The light brown tissue is suberized. Refer to the unit on "Periderm." The vascular bundles are of the open type.

As with other vines, moonseed increases in girth slowly, characteristically has wide rays, its phloem becomes crushed as new phloem is generated each year, and the vascular bundles migrate to the inside of the stem where growth in girth occurs.