'Myrtle trees' in the Bible

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

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.