  A comparative study of spectra of 21 Type Ia supernovae (SNe Ia) obtained
about one week before maximum light, and 8 spectra obtained 11 or more days
before maximum, is presented. To a large extent the premaximum spectra exhibit
the defining characteristics of the four groups defined in Paper II
(core-normal, broad-line, cool, and shallow-silicon). Comparisons with SYNOW
synthetic spectra show that all strong features and most weak ones can be
accounted for in a plausible way. The issues of detached high-velocity
features, the possible ubiquity of carbon clumps, the maximum detectable ejecta
velocities, and the possibility of blueshifted emission-line peaks are
discussed.
