Describe characteristics of heartwood.

Explanation

### Step-by-Step Solution:

1. **Definition of Heartwood**:
- Heartwood is the central, non-living part of a tree trunk, which is typically darker and denser than the surrounding sapwood.

2. **Presence of Organic Compounds**:
- Heartwood contains a variety of organic compounds, including oils, aromatic substances, gums, resins, tannins, phenols, and other colored materials.

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