heart·wood 
(härtwd′)
(härtwd′)n.
The older, nonliving central wood of a tree or shrub, usually darker and harder than the younger sapwood. Also called duramen.
- substantiation
- substantival
- substantivally
- substantive
- substantively
- substantiveness
- substantive right
- substation
- substituent
- substitutability
- substitutable
- substitute
- substitution
- substitutional
- substitutionally
- substitutionary
- substitutive
- substrate
- substrative
- substratum
- substruction
- substructional
- substructural
- substructure
- subsumable