Although water vapor densities around natural snow crystals are between ice saturation and a slight excess over water saturation, the above-mentioned experiments were run only at water saturation. Here, we made experiments at saturation ratios less than one with respect to water. The experiments were carried out for growth time of 10 min under isothermal conditions from -12.5 to -16.5°C. Crystals having fern type, dendrite type, stellar type, and broad-branch type branches were grown even below water saturation, contrary to the results obtained thorough the experiments in static chambers (Kobayashi, 1961; Rottner and Vali 1974). As a snow crystal was suspended by applying the upward wind velocity that was adjusted to the terminal fall velocity of the crystal in our tunnel, the growth of these branched planar snow crystals may be ascribed to ventilation that brings fresh environment to the crystal surfaces. The crystal habits were temperature dependent, with habit regime about the fern regime near -14.2°C, which results are in a manner similar to those at water saturation described above. The crystal habits were also dependent on supersaturation ratio: for example, broad branch, stellar, dendrite, and fern forms occurred at -14.1°C as the ratio increased. The crystal diameter and mass and increased with increasing the ratio: the ferns were grown over ice supersaturation of 9%.