The earliest systems of classification used which types of characters?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the types of characters used in the earliest systems of classification in biology.

2. **Identifying the Time Period**: The earliest systems of classification were dominant from around 300 BC to 1830. This period is significant in the history of biological classification.

3. **Recognizing the Classification System**: The classification system used during this time is referred to as the "artificial system." This system is characterized by its simplicity and reliance on easily observable traits.

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