Although the stems of ferns tend to be of only one basic type-the rhizomethere are a number of striking variations known, both in internal structure and in gross morphology. In size alone, rhizomes vary from the massive upright trunks of certain tree ferns down to the almost filiform structures of many filmy ferns. Very few species of ferns have evolved dimorphic stems showing "division of labor." Some do have differentiation into short shoots and long shoots, i.e., those with short internodes and those with long internodes. Where dimorphism occurs, it is associated functionally, as a rule, either with vegetative propagation or with storage. For example, the Ostrich Fern, Matteuccia, has compact, upright, frondbearing stems and elongate, horizontal stems. The latter enable the plant to form large colonies or clones. Similar, but even narrower and more specialized "stolons" are found in some species of sword ferns, Nephrolepis. Most examples of drastically modified stems, such as the strongly flattened rhizomes of Myrmecophila and Lecanopteris or the tuber-like bodies of Nephrolepis, Polypodium, and the plants to be described below, are epiphytic. Furthermore, they seem to be associated with storage and possibly even symbiotic relationships with ants. Indeed, except for those ferns which have obviously solid "tubers," practically all of these plants have been referred to as "ant-plants" or "myrmecophytes," whether or not any obligatory relationships with ants have been observed or experimentally demonstrated. The plant to be described in this article is a little-known epiphyte with dimorphic stems (Fig. 1): ordinary polypodioid rhizomes and drastically modified, "potatolike" hollow tubers. Hagemann (1969, fig. 1) has recently illustrated and described the structure of these tubers in some detail, but he did not concern himself with the broader comparisons of the plant in respect to its other peculiarities and taxonomic relationships. In our investigations of Solanopteris we have discovered a number of distinctive characters which are described here for the first time.