Orchids generally fall into two categories regarding the direction they grow: Sympodial and Monopodial.
SYMPODIAL
Most orchids have a sympodial growth pattern meaning that they produce their new growths from the base of previous growth. Many, but not all, sympodial orchids produce something called pseudobulbs. These bulbs are not real bulbs. Instead they are thick stems where they store moisture and nutrients. Usually a sympodial orchid will have several pseudobulbs which are joined by a rhizome which may or may not be visible between them. Each bulb provides water and nutrients to one or more of the plants leaves. These pseudobulbs can help the plant survive in times of drought and when other nutrients are lacking. Sympodial orchids without pseudobulbs are usually located in regions where nutrition and water are not lacking which is why they do not need pseudobulbs for storage purposes. The roots of a sympodial orchid are developed from below each new growth. Cymbidiums, Dendrobiums and Cattleyas are examples of sympodial orchids.
MONOPODIAL
For an orchid to be considered monopodial, it must grow upwards and its new growth must be an extension of previous growth. Most monopodial orchids grow from a stem which stands upright. The leaves will grow outwards on either side of the same stem, alternating sides in pairs and with spaces in between them. Sometimes monopodial orchids will produce side growths from the leaves and develop into thick leafy plants. Monopodial orchids do not produce pseudobulbs. Instead the orchid stores water and nutrients in its succulent leaves and roots. The monopodial orchid has aerial roots that grow from the sides and base of the plant. The roots of monopodial orchids are produced at intervals between the main stem leaves. The popular Phaleonopsis orchid is an example of a monopodial orchid.
I like this. These orchids are outrageous!