Array won't be filled by Instantiate

Hi guys (and girls ;)),

I just started using Untity and atm I'm fooling around a bit. In this case I'm trying to instantiate grassPrefabs and manage them in an array so I can always check if the player is too far from the grass and it shouldn't be rendered to save ressources, but somehow the array I'm creating stays empty.

I guess the important part is the very last line.

Ty for your help,

RBH

 #pragma strict
 
 //Normales Gras
 public var Gras1Prefab : Transform;
 var grasArray : GameObject[];
 
 //Spieler erstellen
 public var PlayerPrefab : Transform;
 var iPlayerPrefab : GameObject;
 
 //Level innitiieren.
 var newLevel = 1;
 public static var GrasColor:Color = new Color(0f, 1f, 0f, 1f);
 var mapX : int;
 var mapZ : int;
 
 function Start () {
 
 }
 
 function Update () {
     
     //Lade neue Level
 
     if (newLevel==1){
         newLevel=0;
         iPlayerPrefab = GameObject.Find("PlayerPrefab");
         var filePath = Application.dataPath + "/Resources/Textures/Level/Level1.png";
             if (System.IO.File.Exists(filePath)){
                var bytes = System.IO.File.ReadAllBytes(filePath);
                var tex = new Texture2D(1, 1);
                tex.LoadImage(bytes);
                
                iPlayerPrefab.transform.position = Vector3 (5,5,5);
                
                transform.localScale += Vector3(tex.width ,0,tex.height);
                transform.localPosition += Vector3(tex.width/2,0,tex.height/2);
                mapX=tex.width;
                mapZ=tex.height;
                
                //Erstellung von "Normales Gras
                grasArray = Array(tex.width*tex.height);    
                for(var x=0; x<tex.width; x++){
                    for(var z=0;z<tex.height; z++){
                       var pixel:Color = tex.GetPixel(x, z);
                        if (pixel==GrasColor){    //Normales Gras
                            grasArray[x+(tex.width*z)] = Instantiate (Gras1Prefab, Vector3(x,1,z), Gras1Prefab.transform.rotation) as GameObject;
                        }
                    }
                }
         }
     }