WebcamTexture not playing when called with button click event

I've attached the script below to an image on a canvas. That canvas also has a play and stop button.

Okay, so the code below starts the webcam and records just fine when I call it with StartCoroutine(play()) from the Start function. However, when I press a "play" button and call OnPlay(), which in turn calls the same coroutine as I call in the Start() function, it doesn't play. I've traced that the button is actually calling the right function, but I get all "false" results for those isPlaying traces when I do it that way. Any idea what would cause this?

If you're wondering why I'm using a coroutine, it's because it seems to need a slight delay before I start playing and mapping it to the canvas.

The stop button / OnStop() function works fine in all cases.

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3. using UnityEngine.UI;
4. using System.Collections.Generic;
5.  
6. public class WebcamRecorder : MonoBehaviour {
7.         private WebCamTexture _webcamTexture;
8.         public List<Color32[]> data;
9.     // Use this for initialization
10.     void Start () {
11.                 data = new List<Color32[]> ();
12.                 _webcamTexture = new WebCamTexture ();
13.                 StartCoroutine (play());   //WORKS
14.     }
15.  
16.     // Update is called once per frame
17.     void Update () {
18.                 //Debug.Log ("isPlaying" + _webcamTexture.isPlaying);
19.                 if (_webcamTexture.isPlaying)
20.                     data.Add (_webcamTexture.GetPixels32 ());
21.  
22.     }
23.  
24.     public void OnPlay()
25.     {
26.                 Debug.Log("web cam texture " + _webcamTexture);
27.                 StartCoroutine(play());   //DOESN'T WORK
28.                 Debug.Log ("playing " + _webcamTexture.isPlaying);
29.     }
30.  
31.         IEnumerator play()
32.         {
33.              
34.             Debug.Log ("trying " + _webcamTexture.isPlaying);  
35.             _webcamTexture.Play ();
36.             Debug.Log ("trying2 " + _webcamTexture.isPlaying);  
37.             yield return new WaitForSeconds (0.1f);
38.             GetComponent<Image> ().canvasRenderer.SetTexture (_webcamTexture);
39.             Debug.Log ("trying3 " + _webcamTexture.isPlaying);  
40.                      
41.         }
42.  
43.     public void OnStop()
44.     {
45.             //yield return new WaitForSeconds (10f);
46.             _webcamTexture.Stop ();
47.             Debug.Log ("pixel length:" + data.Count + " one entry size: " + data[0].Length);
48.  
49.     }
50. }
51.