THREE RHYMING RIDDLES

1)
What's in rock, but not in stone,
That's found in marrow, but not in bone;
It's in the bolster, but not the bed,
It's neither living nor is it dead.

2)
My first is an heir,
My second a snare;
My whole the offspring of a poet's musing.
Perhaps some day
I'll give it away
To  someone special of my choosing.

3)
Both a mother who never gave birth,
And a father of little worth,
I have no mind and never ponder,
I'm rarely still, but never wander.


Answers:

1. The letter "R". 
2. Sonnet
3. Tree