I OFTEN pass a gracious tree  
Whose name I can't identify,  
But still I bow, in courtesy  
It waves a bough, in kind reply. 
 
I do not know your name, O tree  
(Are you a hemlock or a pine?)  
But why should that embarrass me?  
Quite probably you don't know mine.
Christopher Morley
http://www.poemhunter.com/poem/tit-for-tat-5/