<jats:p> Corydalis sempervirens has yielded six alkaloids, two of which, bicuculline and bicucine, had been previously lound in Dicentra cucullaria. The similarity of these two plants is further demonstrated by the presence in the former of cryptopine and, as in the case of other fumaraceous plants, protopine. A new alkaloid. C<jats:sub>19</jats:sub>H<jats:sub>17</jats:sub>O<jats:sub>6</jats:sub>N(?), which has been named capnoidine appears to be isomeric with adlumidine but is not identical with it. A very small amount of an unidentified base melting at 201 °C. was also obtained.