'Myrtle trees' in the Bible

I saw in the night, and, behold, a man riding upon a red horse, and he stood among the myrtle-trees that were in the bottom; and behind him there were horses, red, sorrel, and white.

And the man that stood among the myrtle-trees answered and said, These are they whom Jehovah hath sent to walk to and fro through the earth.

And they answered the angel of Jehovah that stood among the myrtle-trees, and said, We have walked to and fro through the earth, and, behold, all the earth sitteth still, and is at rest.