code: function(features, options) {
          var all = (features == undefined); // evaluates to true if
                                             // features is null
          if(all) {
              features = this.features;
          }
          if(features) {
              this.removeFeatures(features, options);
              for(var i=features.length-1; i>=0; i--) {
                  features[i].destroy();
              }
          }
      }
docs: APIMethod: destroyFeatures
  Erase and destroy features on the layer.
  
  Parameters:
  features - {Array(<OpenLayers.Feature.Vector>)} An optional array of
  features to destroy.  If not supplied, all features on the layer
  will be destroyed.
  options - {Object}