You guys can "kick" me but the term bulb is not a good term when used with aroids.
Here's what I recently learned while doing some major research for an article that will be in the next issue of Aroideana. All of this info came about after nearly a month of discussions with some real experts.
A bulb is an underground storage structure that is a condensed stem usually with a basal plate and fleshy storage leaves surrounding the bud that will form the next plant. This type of stem occurs in many plant families but not in the Araceae (aroids).
The stem of a plant is the central axis or base of the plant and not the stalk that supports any single leaf. A stem is normally divided into nodes and internodes. The nodes often produce a complete leaf with a petiole as well as producing roots and buds which may grow into shoots of various forms. The stem's roots anchor the plant either to the ground, a tree or to a rock. As you can see from this definition the word "stem" is not applicable to the part of a leaf correctly known as the petiole.
A bulbil is a name used for reproductive structures such as those formed in the junction of veins in some Amorphophallus species. It is a useful word that can be used without defining it much more precisely.
A bulblet forms at the juncture of the petiole and the stem in only a very few aroids including the ZZ. That little bublet is just a very tiny stem which allows a leaf that falls to the ground to form an entirely new plant.
A corm is an underground stem to which the above-ground parts of the plant may die back in the dormant season. It often stores starch and when it regrows, foliage will come from the top, and roots from the base like a typical stem. There are no true examples of a corm in the aroid family.
A tuber is an underground structure which is almost entirely a starch storage organ. The buds for future growth and the roots all develop at the apex (“top”) when the tuber forms as the tip of a stolon which it often but not always does. In Amorphophallus, Arum and Typhonium the stem tissue is encased in the small bud at the top of the tuber full of stored food.. That bud grows upward into a leaf or two and outward into roots with the tuber beneath.
Based on info from Dr. Croat and other scientists tuber is the most applicable term for an aroid but bublet does apply in some genera. Tuber would therefore be the correct term for what we often like to call a "bulb".
I hope I've not just confused the blazes out of everyone! If I have then LariAnn can explain it to all of us!
Steve
