HI at 6297 cm$^{-1}$ (1.5881 $\mu$m).

The behavior of the molecular features is illustrated for both the second–overtone $^{12}$CO (6,3) and the OH ($\Delta v = 2$) indices. Both indices exhibit a similar behavior with temperature and luminosity, becoming detectable around $T_{eff}$ = 5000, with a strength in the giants approximately twice that in the dwarfs. Similar behavior was noted by KH86 in the first–overtone CO features in the K–band. In dwarf stars the second–overtone CO index reaches a maximum before M5, and displays a turnover toward the coolest stars. This may be due in part to features of CaI and FeI which contaminate the index for intermediate spectral types (F5–K3). Ali et al. (1995) find that the relationship between T$_{eff}$ and equivalent widths of the first–overtone CO bandheads flatten out between 3500–5000 K in dwarf stars. From high resolution ($R > 45,000$) FTS spectra, Wallace & Hinkle (1996) observed that the 2 $\mu$m continuum in late–type dwarf stars is suppressed by numerous water vapor features which are blended at intermediate to low resolution. Predicting the equivalent widths of features where the apparent continuum is subject to temperature and luminosity effects is not straight–forward. In contrast, both the CO and 