Onions + Christmas Trees

A family is at the dinner table.
The son asks his father, 'Dad, how many kinds of boobs are there?
The father, surprised, answers, 'Well, son, there are three kinds of
boobs:
In her 20's, a woman's are like melons, round and firm.
In her 30's to 40's, they are like pears, still nice but hanging a bit.
After 50, they are like onions'.
'Onions?'
'Yes, you see them and they make you cry.'
This infuriated his wife and daughter so the daughter said, 'Mum, how
many kinds of 'willies' are there?.
The mother, surprised, smiles and answers, 'Well dear, a man goes
through three phases.
In his 20's, his willy is like an oak tree, mighty and hard.
In his 30's and 40's, it is like a birch, flexible but reliable.
After his 50's, it is like a Christmas Tree.'
'A Christmas tree?'
'Yes - the tree is dead and the balls are just for decoration.'