The lengthening of the vowel takes place in the case of a aṅga (stem) ending in a vowel, as well as of han and gam when the Desiderative affix san being jhalādi (i.e. not taking the augment iṭ) follows.,
Thus of roots ending in vowel we have :- विवीषति, तुष्टूषति, चिकीर्षति, जिहीर्षति 7.1.100; of हन् and गम्, जिघांसति, and अधिजिगांसते ॥
Vart:- The rule applies to that गम् which is the substitute of इङ् 2.4.48 'to study'. Therefore, not here, संजिगंसते वत्सो मात्रा (cf. 7.2.58); In the Veda we read स्वर्गे लोकं समजिगांसत्, where though गम् means 'to go' and is not, therefore, the substitute of इङ्, the lengthening takes place by the rule 6.3.137. Or the word अच् should not be added in the sutra at all: which should be read as हनगमां सनि meaning \There is lengthening of the stem when the Desiderative सन् follows\. This would apply of course, to vowel-ending stems, because the sentence would mean that, for there cannot be lengthening of a consonant. This will apply to गम् also, in this way :-\ A stem ending in a vowel is lengthened in the Desiderative, and so also of गम् which is a substitute of the vowel-stem इ\ ॥ In this way, we may see, that there is no necessity of the Vartika.,