Why do all gameobjects not dissapear from view when I switch cameras?

I am having trouble with camera switching. I have two cameras: "Camera1" and "Camera2". A "button script" attached to Camera1 allows a switch to Camera2. It also positions the cameras. There is a gameobject called "Main Menu" that is meant to be a background image for the button ; it is a GUI texture background (a flat jpeg image) .

At game start, the button works (sort of!) ; clicking it causes "Camera" components to be enabled and disabled appropriately, and it changes the game view background.

Problem: the GUI texture does not disappear from game view, and nor does the button!

When I click the button, I want a complete change of game view, i.e., I want both the button and its GUI texture background to disappear from game view. But I am not getting that. I would appreciate any help to understand why.

How can I make a GUI texture visible ONLY because it is in front of Camera1? How do I make the button visible ONLY when Camera1 is active?

Here is my button script:

      using UnityEngine;
      using System.Collections;

 public class PageButton : MonoBehaviour
 {
 public GameObject MainMenu ;
 public Camera cam1, cam2 ;
 void Start() {
 // position the Main Menu
     MainMenu = GameObject.Find("MainMenu"); 
     MainMenu.transform.position = new Vector3 (0, 0, 0);

 // Setup Camera1
     cam1 = GameObject.Find("Camera1" ).GetComponent<Camera>() as Camera;
     cam1.transform.position = new Vector3 (0, 0, -10);
     cam1.orthographic = true;
     cam1.orthographicSize = 5f;
     cam1.enabled = true;

 // Setup Camera2
     cam2 = GameObject.Find("Camera2" ).GetComponent<Camera>() as Camera;
     cam2.transform.position = new Vector3 (100, 100, 10);
     cam2.enabled = false;
     cam2.transform.Rotate(0,270,0, Space.World);
     cam2.orthographic = true;
     cam2.orthographicSize = 5f;
 }

 public void OnGUI()
 {  
     if(GUI.Button(new Rect(580,340,20,20), ">")) {
         Debug.Log ("Button pressed");
         cam1.enabled = false;
         cam2.enabled = true;
     }  

 } // end OnGUI()

 


 } // end PageButton