A set of spectrograms of Me variables is reproduced in order to separate the effects produced by several of the physical parameters that characterize their atmospheres. 1. For M giants later than MS, the spectral types will more accurately give a temperature sequence if they are obtained from relative strengths of molecular bands (TiO and VO) rather than from absolute intensities. The reason is that even the vibrational levels of TiO are far enough apart to have appreciably different populations at temperatures of 3000 K and lower. 2 In certain Mira variables later than MSe, consistent differences appear in the ratios of the bands of YO, ScO, AlO, and TiO, which appear to reflect real differences in the relative abundances of these metals. Strengthening of YO and ScO indicates a tendency toward spectral type S; in such stars, AlO is often weak. 3. Mira variables consistently show weaker absorption lines than do other M-type giants of the same types The strong lines of most neutral atoms are the ones most weakened in Miras earlier than M6e at maximum light. In these members of the high-velocity population the line weakening suggests a metal deficiency of order 10- . 4. In the spectra of the low-velocity population comprising most Mira variables later than MSe at maximum light, the line weakening is generally less conspicuous and may vary greatly from cycle to cycle. While part of this line weakening can be explained by a metal deficiency of the order of 10-', an important part must also be due to other causes, such as variable opacity due to continuous absorption by TiO and other molecules.