The Pbcm and A21am C31H64, and P21/c and P2/c C30H61OH unit cell models were built by extending the repeating pattern of carbon atomic coordinates in reported structures for shorter chain hydrocarbons. The Pbcm C31H64 structure was adapted from the structure for tricosane (C23H48) reported by Smith. The A21am C31H64 was in turn adapted from the carbon spacings in the Pbcm cell by shifting the atomic coordinates to the symmetric positions outlined for alternative setting Bb21m by Lüth et al. followed by necessary axis adjustments. Lattice parameters were defined for the Pbcm and A21am unit cells using experimental data. The C2/c C30H61OH structure was adapted from the structure for n-eicosanol (C20H41OH) reported by Michaud et al. The P21/c C30H61OH structure was adapted from the structure for 1heptadecanol (C17H35OH) reported by Seto. The P2/c C30H61OH structure was adapted from the Pbcm unit cell by reducing the space group symmetry and asymmetric substitution of the terminal C for O. The lattice parameters for the P21/c and C2/c unit cells were calculated by extending the unit cells so that the previous C-C and O-O distances (in Å) were retained. For zone axis pattern simulations (Figures S5, S6 and S8) electron diffraction patterns were simulated using SingleCrystal, part of the CrystalMaker software. For patterns away from high symmetry zone axis orientations (Figure ), electron diffraction patterns were simulated using the DiffSims package as part of Pyxem to incorporate effects of the Ewald sphere. Crystal orientations in simulations were defined by the unit cell direction [UVW] along the electron beam trajectory.