Continuing from the last post on the sigmatic aorist in Latin, I turn to Bridget Drinka’s examination of this matter in Old Church Slavonic. This will be brief, due to being occupied by other matters at university.
While Drinka shows that the sigmatic aorist in Latin is in general a very late innovation, her goal for Slavonic is to show that the lengthened grade, traditionally reconstructed for a sigmatic aorist in Proto-Indo-European, is a Slavonic innovation. We can suppose that lengthening of the root vowel occurs due to the loss of the some consontant alone, since Slavonic adopted such strict rules for compounds, and there is no need to suppose such a grade in the proto-language. To take the verb rešti, for example, we see that in the infinitive there is no lengthening, but in the aorist rěše there is. This final form could have come through application of ruki—which, as Drinka explains, was a wandering innovation slowly spreading across the eastern IE languages—from earlier rēs-, which in turn has it lengthened vowel due to the loss of the velar in the proto-form *rek-s.