Praudhamanorama p219

p219

[On] "vṛddhyautva...": In "atisakhīni kulāni", vṛddhi was applicable due to treatment like a ṇ-it affix by "sakhyurasambuddhau"; in "vāriṇi", however, autva was applicable by "acca gheḥ"; in "priyakroṣṭūni" and so on, treatment like tṛc was applicable.
If it is asked, "What is the difference between num and nuṭ?", to that he says: "nāmi". But since num is an augment belonging to the stem, if it occurred, lengthening would not take place: this is the purport.
[On] "tṛtīyādiṣu" (Pāṇini 7.1.74): [On] "puṃvat": By implication, this is a prohibition of num and shortening.
[On] "pravṛttinimittabhedāt" [due to the difference in the ground for application]: For, in the case of the word "pīlu", the ground for application to a tree is the universal subsumed under tree-ness, whereas in the case of the fruit it is the universal subsumed under fruit-ness, or being produced by that particular tree. In either case, the ground for application is not one and the same for the masculine and the neuter: this is the purport.