Reference for Oktzin 2:3
הָרִמּוֹן וְהָאֲבַטִּיחַ שֶׁנִּמּוֹק מִקְצָתוֹ, אֵינוֹ מִצְטָרֵף. שָׁלֵם מִכָּאן וּמִכָּאן וְנִמּוֹק מִן הָאֶמְצַע, אֵינוֹ מִצְטָרֵף. הַפִּטְמָא שֶׁל רִמּוֹן, מִצְטָרֶפֶת. וְהַנֵּץ שֶׁלּוֹ אֵינוֹ מִצְטָרֵף. רַבִּי אֱלִיעֶזֶר אוֹמֵר, אַף הַמַּסְרֵק טָהוֹר:
Regarding a pomegranate or melon, part of which has rotted, it [i.e. the rotten part] does not join together [with the rest of the food, to count towards the measure of impurity]. If it is whole on either side, and rotten in the middle, it does not join together [and even the sides are not joined to each other]. The stem of a pomegranate does join together [to the rest of the fruit], and its flower does not join together. Rabbi Elazar says: even the crown [literally: the comb, around the stem] is pure [and does not join together].