The vṛddhi is the single substitute when the augment āṭ is followed by any vowel.,
The anuvritti of एचि ceases : that of अचि however, is present. The vowel that is subsequent to the augment आट्, and the आट् which is precedent to a vowel-in the room of these two i. e. the आट् and the vowel-subsequent and precedent, the Vriddhi is the single substitute. The augment आट् is added to the roots beginning with a vowel, in the Imperfect, Aorist and Conditional Tenses 6.4.72 &c)). Thus ऐक्षिष्ट, ऐक्षत, ऐक्षिष्यत, औभीत्, और्द्ध्रीत्, औब्जीत् from roots ईक्षदर्शने (Bhvadi. 641), उभ उम्भ पूरणे (Tudadi. 32) and उ ब्ज आर्जवे (Tudadi. 20). According to Siddhanta Kaumudi the आट् is the augment which ङित् case-affixes take after nadi-words 7.3.112. According to him the following are the examples:- बहुश्रेयसी + आट् + ङे = बहुश्रेयस्यै (Dative Singular). The आट् is the augment also in the Vedic Tense लेट् ॥
The च् 'and' in the sutra shows that the पररूप rule, taught in 6.1.95, 6.1.96 when उस्, ओं and आङ् follow, is superseded, when the preceding vowel is आट् ॥ Thus औस्रीयत्, औकारीयत् ॥ आ + ऊढा = ओढा, तामैच्छत् = औढीयत् ॥,