What is thorn? How can you tell it is modified stem?

Explanation

### Step-by-Step Solution:

1. **Definition of Thorn**:
- A thorn is defined as a hard, sharp-pointed structure that is primarily found on certain plants. Its main function is to provide protection against herbivorous animals that may graze on the plant. Additionally, thorns help in reducing the rate of transpiration, which is the loss of water from the plant.

2. **Identification as a Modified Stem**:
- To determine that a thorn is a modified stem, we can observe certain characteristics:
- **Presence of Buds**: Thorns typically bear buds in their axils. This is a key feature that indicates they are modified stems, as true leaves do not have this characteristic.
...