The pseudobulb is a storage organ derived from the part of a stem between two leaf nodes.
It applies to the orchid family (Orchidaceae), specifically certain groups of epiphytic orchids, and may be single or composed of several internodes with evergreen or deciduous leaves along its length.
In some species, it is hardly swollen at all and looks like a normal stem with many leaves while at the other extreme, some genera such as Bulbophyllum have single, spherical pseudobulbs with one leaf at the apex of each.
Whether cane-like (with many joints) or spherical (with one or few joints), they are all produced from a long lived creeping stem called a rhizome which may itself be climbing or pendulous.
The pseudobulbs are themselves relatively short lived (1-5 years), but are continually produced from the growing tip of the rhizome.
The other growth habit used by tropical epiphytic orchids is known as monopodial.