Birth of Tulsi and Salagram
Vishnu wanted to proclaim to the world the virtue of his devotee by making her immortal and divine. He made her body flow as a river and converted her energy into a plant on the bank of the river.The river was named Gandak and the plant, was called Tulsi. To bless her always with his grace, Vishnu manifested himself as a black spherical (salagram) and took his abode in the river
Thus Vishnu as salagram and Brinda as tulsi became inseprable.
There is a village in Nepal by the name Salagram. The river Gandak flows through the place, On the banks Tulsi plants grow as thick bushes.