Visuddhimagga XIV-51

Sasambhārajivhāmajjhassa upari uppaladalaggasaṇṭhāne padese jivhā yathāvuttappakārupakārupatthambhanānupālanaparivārā jivhāviññāṇādīnaṃ yathārahaṃ vatthudvārabhāvaṃ sādhayamānā tiṭṭhati.

「舌（根）」──在全体的舌的中央的上部，即在那像莲的花瓣的前部的形状的地方，它的资助、支持、保护、随从，已如前述，它恰好是舌识等的所依和门。

Ñ(XIV,51): 4. The tongue [sensitivity] is to be found in the middle of the [feature of the] tongue with its accessories in the place shaped like a lotus petal tip. It has assistance, consolidation and maintenance in the way aforesaid; and it duly serves both as physical basis and as door for tongue-consciousness, and the rest.