Characteristics of striations-the onset current for the excitation of waves, the dispersion, the velocity, the waveform, nonlinearities and the gas temperature dependence-are studied in tubes with diameters 1.0 to 3.0 mm in He, Ne and their mixtures. Only hydrodynamic modes are excited. As the tube diameter is reduced, both the wave number and the angular frequency increase. For a given diameter, there is a critical pressure below which waves cannot be excited. Similarity rules hold for the onset current, but not for the frequency. Discreteness in frequency appears strongly for the excitation of striations. Also, an increase in gas temperature affects the striations, especially at lower pressure and higher currents: the wave frequency increases and its amplitude decreases. The observed characteristics are found to be consistent with the results derived from the macroscopic equations.