Spectroscopically peculiar Type Ia supernovae and implications for progenitors

In a recent paper Li et al. reported that 36% of 45 Type Ia supernovae (SNe Ia) discovered since 1997 in two volume-limited supernova searches were spectroscopically peculiar, and they suggested that because this peculiarity rate is higher than that reported for an earlier observational sample by Branch et al., it is now more likely that SNe Ia are produced by more than one kind of progenitor. In this paper I discuss and clarify the differences between the results of Li et al. and Branch et al., and I suggest that multiple-progenitor systems are now less likely than they were before.