According To definition of Lichens: Lichens are symbiotic associations of a fungus with the photosynthetic partner called as phycobiont such as green algae or cyanobacteria.gain, The two organisms live in close association with each other and both get benefit from this kind of association, this is called Symbiotic Association. By the way, Parasitic relation means living in or on another organism (host) and causing harm to it.
The White Nile (Arabic: Ø§ÙÙÙÙ Ø§ÙØ£Ø¨ÙØ¶ââ an-nÄ«l al-'abyaá¸) is a river in Africa, one of the two main tributaries of the Nile; the other is the Blue Nile. In the strict meaning, White Nile refers to the river formed at Lake Victoria, at the confluence of the Bahr al Jabal and Bahr el Ghazal Rivers.
Two main ones - the Blue Nile and the White Nile.   The major tributaries are:   TheWhite nile & The Blue nile. In fact, it is said that the Nile River has only two tributaries. It is not exact and so there may be more.