Nodes in Spherical Harmonics

In Rydberg Atoms book by Thomas F. Gallagher, Page 14, the author provides the general equation of spherical harmonics which is well-known. He states that there exist $l-m$ nodes in the $theta$ coordinate, and none in the $phi$ coordinate. The coordinate system taken by the author is given below in the figure.

I understand the concept of nodes and how to count them for each orbital. I am trying to visualize the direction of these nodes but I cannot understand how these nodes are in the $theta$ coordinate not in the $phi$ coordinate.