to a maximum (at a peak equivalent width of $\sim$ 3 cm$^{-1}$) as $T_{eff}$ approaches 10000 K, and a slower decline toward higher temperatures. The behavior of the index is similar in both the dwarfs and the giants, although the luminosity class I/II sources show a larger scatter, presumably due to intrinsic variability (e.g. Kaufer et al. 1996). The general behavior of the neutral atomic features is illustrated by the Mg6345 index. In luminosity classes IV–V, this index reaches a maximum strength between 5000-6000 K, with a peak equivalent width of $\sim$ 2.5 cm$^{-1}$. In contrast, the maximum strength of this index in the lower surface gravity objects (also $\sim$ 2.5 cm$^{-1}$) is found in the coolest stars in our sample, monotonically decreasing toward higher temperatures; as expected given the behavior of ionization state as a function of surface gravity. The two SiI indices exhibit similar behavior, but the AlI index, (not shown) turns over at much lower temperatures in our dwarf stars because of its lower ionization potential. Note that we have chosen not to form an index based on the strongest SiI line at 6292 cm$^{-1}$ (1.5892 $\mu$m) because it is coincident with the 4–14 Brackett line of 