Before the case-ending os , e is substituted for the final a of Nominal-stem.,
As वृक्षयोः (Genitive dual) स्व, प्लक्षयोः स्वम्, वृक्षयोः (Locative dual) as वृक्षयोर्निधेहि, प्लक्षयोर्निधेहि ॥,
Adhyāya 7 · Pāda 3 · Rule 104
Before the case-ending os , e is substituted for the final a of Nominal-stem.,
As वृक्षयोः (Genitive dual) स्व, प्लक्षयोः स्वम्, वृक्षयोः (Locative dual) as वृक्षयोर्निधेहि, प्लक्षयोर्निधेहि ॥,