Passage 5.14.3
εἶχον δὲ ἄρα καὶ ἐξ ἀρχῆς οἱ ποταμοὶ καὶ ἐς τόδε ἔχουσιν οὐ κατὰ τὰ αὐτὰ ἐπιτηδείως πρὸς γένεσιν πόας τε καὶ δένδρων· ἀλλὰ πλεῖσται μὲν ὑπὸ Μαιάνδρου μυρῖκαι καὶ μάλιστα αὔξονται, Ἀσωπὸς δὲ ὁ Βοιώτιος βαθυτάτας πέφυκεν ἐκτρέφειν τὰς σχοίνους, τὸ δένδρον δὲ ἡ περσεία μόνου χαίρει τοῦ Νείλου τῷ ὕδατι. οὕτω καὶ τὴν λεύκην θαῦμα οὐδὲν καὶ αἴγειρόν τε καὶ κότινον, τὴν μὲν ἐπὶ Ἀχέροντι ἀναφῦναι πρώτῳ, κότινον δὲ ἐπὶ τῷ Ἀλφειῷ, τὴν δὲ αἴγειρον γῆς τῆς τῶν Κελτῶν καὶ Ἠριδανοῦ τοῦ Κελτικοῦ θρέμμα εἶναι.
From the beginning, rivers have had, and still have now, different qualities, each suited differently to nourishing grasses and trees. Thus, great numbers of tamarisks grow most abundantly beside the Maeander; the Boeotian Asopus is naturally best at growing the tallest reeds; and as a tree, the Egyptian persea delights solely in the waters of the Nile. So too, there is nothing surprising in the fact that the white poplar first appeared beside the Acheron, the wild olive by the Alpheius, and that the black poplar should be native to the land of the Celts and the Celtic Eridanus.