Corm

[1] A corm consists of one or more internodes with at least one growing point, generally with protective leaves modified into skins or tunics.

They act as a covering, protecting the corm from insects, digging animals, flooding, and water loss.

For example, some of the larger species of Watsonia accumulate thick, rot-resistant tunics over a period of years, producing a structure of tough, reticulated fibre.

[2] Internally, a typical corm mostly consists of parenchyma cells, rich in starch, above a circular basal node from which roots grow.

Corms are stems that are internally structured with solid tissues, which distinguishes them from bulbs, which are mostly made up of layered fleshy scales that are modified leaves.

In most places where geophytes are common, so are animals that feed on them, whether from above like pigs, or from below like bulb weevils, mole rats, or pocket gophers.

Such animals eat through protective tunics, but they generally miss several cormels that remain in the soil to replace the consumed plant.

In some other species, contractile roots seem to be a defence against digging animals and can bury the corm surprisingly deeply over the years.

Wurmbea marginata[4] is one example of a small plant that can be challenging to dig unharmed out of a hard, clayey, hillside.

Taro corms for sale in a Réunion market
Crocosmia corm with the tunic partly stripped to show its origin at the nodes on the corm cortex.
Crocosmia corm anatomy, showing tunic, cortex of storage tissue, central medulla, and emergence of a new corm from a bud near the top.
Crocosmia corm with stolons emerging through the tunic. The stolons originate at the axillary buds of the corm scales, and generally produce new corms at their tips
Gladiolus corm, showing the formation of small cormels at the ends of short stolons
Corm on Alocasia macrorrhizos