We have described previously the isolation of four kinds of indole alkaloids, gardneramine, gardnerine, gardnutine and hydroxygardnutine from the dry roots and stems of Gardneria nutans Sieb. et Zucc. (HEraikazura). From the following chemical and spectroscopical data, structures of gardnerine, gardnutine and hydroxygardnutine were elucidated to be I, II, and III, respectively. Gardnerine(1): m.p. 243-244°, C20H24O2N2·H2O, (α) -29.4, Pka 7.36, UV λ MeOH max (log ε); 228.5, 268.5 and 298 (4.56, 3.70 and 3.77) (2,3-disubstituted 6-methoxyindole chromophore). Presence of functional groups (1×double bond, 1×C-OH, 1×OCH3 and 1×C-CH3) was evidenced by acetylation, catalytic reduction and Kuhn-Roth method experiments. NMR spectrum of its mono-acetate indicated ethylidene and methoxy groups; mass spectrum showed strong peaks at m/e 324(M+ 56%), 323(M-1 57%), etc. Treatment with p-toluenesulfonylchloride gave indolenine derivative(IV), which was transformed to indoline derivative(V) by LiAlH4 reduction and reverted to IV by Pb(OAc)4 oxidation. Oxidation with CrO3-H2SO4 gave VIII and IX, with VIII converting to IX under strong acid and IX regenerating gardnerine by LiAlH4 reduction. Gardnutine(II): m.p. 319-320°, C20H22O2N2(M+; 322), (α) +30.3, Pka 5.77. Its UV and IR spectra matched gardnerine's oxidation product IX, confirmed by mixed melting point and optical rotation. Hydroxygardnutine(III): m.p. 311-312°, C20H22O3N2(M+; 338), (α) +36.2, Pka 5.64, IR ν KBr max cm⁻¹; 3200 and 3580, functional groups included OCH3 and C-OH (monoacetate formed). UV spectrum similar to I and II. LiAlH4 reduction gave dihydroxy derivative(X); hydrogenolysis gave 19,20-dihydrogardnutine(XI), also from catalytic hydrogenation of II. Oxidation with MnO2 gave α,β-unsaturated aldehyde(XII), which regenerated III by NaBH4 reduction. A part of the expense of this work was supported by a Grant-in-Aid from the Ministry of Education, Japan.