MORPHOGENESIS OF THE PROTOCORM OF CYPRIPEDIUM ACAULE (ORCHIDACEAE)

The nature of the protocorm of the Orchidaceae has fascinated morpholo gists for more than a century. In the present study, the development o f the protocorm was followed using in vitro germination of seeds on a culture medium containing sugar, but without a symbiont. Inside the se ed, the embryo consists of about a hundred cells. In the embryo, cells are arranged along a longitudinal axis according to size; these cells contain protein and lipid reserve material. In the first stages of se edling development, the embryo is transformed into a protocorm and mer istematic tissue becomes organized into a meristematic dome (''promeri stem'') at the anterior pole. This meristematic dome will Five rise to a scale and the apex of the seedling. At first, the apex and the scal e leaf develop synchronously. The development of the root always follo ws that of the apex. The study of the development of the seed of Cypri pedium acaule showed that the protocorm is a distinct morphological sy stem with respect to the rest of the cormus. The protocorm may be inte rpreted as an extension of the proembryonic stage.