A survey of some chemical constituents of the lycopods was carried out in order to determine whether the chemistry of these plants is correlated with their taxonomy. One approach to this problem was to study the products of photosynthesis of species of Lycopodium. Selaginella and Isoetes. Radioactive C¹⁴O₂ was to fed these plants and the distribution of radioactivity in sugars and amino acids was examined by means of paper chromatography. The distribution of radioactivity in sugars was characteristic for each genus, but the distribution of radioactivity in amino acids was not. In Selaginella 80% or more of the radioactivity was incorporated into trehalose while most of the rest of the radioactivity was found in sucrose. There was one exception to this: in S. kraussiana 40% of radioactivity was incorporated into trehalose while most of the rest was incorporated into an unidentified sugar. In Isoetes 4% to 8% of the radioactivity was found in trehalose with most of the rest in sucrose. In Lycopodiurn 95% or more of the radioactivity was found in sucrose and none was found in trehalose. Radioactive trehalose was administered to species of these genera and it was shown that they are all able to metabolize trehalose to some degree. Species of Selaginella, Isoetes and Phylloglossum were examined to determine whether they contain alkaloids. Phylloglossum extracts contained compounds with the chromatographic properties of Lycopodiurn alkaloids, but Selaginella and Isoetes species did not contain detectable amounts of these compounds. / Science, Faculty of / Botany, Department of / Graduate