diff --git a/lib/less/tree/mixin.js b/lib/less/tree/mixin.js
index 2908d981..fbb6780e 100644
--- a/lib/less/tree/mixin.js
+++ b/lib/less/tree/mixin.js
@@ -109,7 +109,6 @@ tree.mixin.Definition.prototype = {
         this.rules = visitor.visit(this.rules);
         this.condition = visitor.visit(this.condition);
     },
-    toCSS:     function ()     { return ""; },
     variable:  function (name) { return this.parent.variable.call(this, name); },
     variables: function ()     { return this.parent.variables.call(this); },
     find:      function ()     { return this.parent.find.apply(this, arguments); },
diff --git a/lib/less/tree/negative.js b/lib/less/tree/negative.js
index 3342d82e..e36b6084 100644
--- a/lib/less/tree/negative.js
+++ b/lib/less/tree/negative.js
@@ -9,11 +9,10 @@ tree.Negative.prototype = {
         this.value = visitor.visit(this.value);
     },
     genCSS: function (env, output) {
-        output.add(this.toCSS(env));
-    },
-    toCSS: function (env) {
-        return '-' + this.value.toCSS(env);
+        output.add('-');
+        this.value.genCSS(env, output)
     },
+    toCSS: tree.toCSS,
     eval: function (env) {
         if (env.isMathOn()) {
             return (new(tree.Operation)('*', [new(tree.Dimension)(-1), this.value])).eval(env);
diff --git a/lib/less/tree/operation.js b/lib/less/tree/operation.js
index 807d8f88..8909f14f 100644
--- a/lib/less/tree/operation.js
+++ b/lib/less/tree/operation.js
@@ -35,12 +35,17 @@ tree.Operation.prototype = {
         }
     },
     genCSS: function (env, output) {
-        output.add(this.toCSS(env));
+        this.operands[0].genCSS(env, output);
+        if (this.isSpaced) {
+            output.add(" ");
+        }
+        output.add(this.op);
+        if (this.isSpaced) {
+            output.add(" ");
+        }
+        this.operands[1].genCSS(env, output)
     },
-    toCSS: function (env) {
-        var separator = this.isSpaced ? " " : "";
-        return this.operands[0].toCSS() + separator + this.op + separator + this.operands[1].toCSS();
-    }
+    toCSS: tree.toCSS
 };
 
 tree.operate = function (env, op, a, b) {
diff --git a/lib/less/tree/paren.js b/lib/less/tree/paren.js
index 3bd65d41..e27b8d66 100644
--- a/lib/less/tree/paren.js
+++ b/lib/less/tree/paren.js
@@ -10,11 +10,11 @@ tree.Paren.prototype = {
         this.value = visitor.visit(this.value);
     },
     genCSS: function (env, output) {
-        output.add(this.toCSS(env));
-    },
-    toCSS: function (env) {
-        return '(' + this.value.toCSS(env).trim() + ')';
+        output.add('(');
+        this.value.genCSS(env, output);
+        output.add(')');
     },
+    toCSS: tree.toCSS,
     eval: function (env) {
         return new(tree.Paren)(this.value.eval(env));
     }
diff --git a/lib/less/tree/quoted.js b/lib/less/tree/quoted.js
index 188cc2bb..e78accad 100644
--- a/lib/less/tree/quoted.js
+++ b/lib/less/tree/quoted.js
@@ -10,15 +10,15 @@ tree.Quoted = function (str, content, escaped, index, currentFileInfo) {
 tree.Quoted.prototype = {
     type: "Quoted",
     genCSS: function (env, output) {
-        output.add(this.toCSS(env));
-    },
-    toCSS: function () {
-        if (this.escaped) {
-            return this.value;
-        } else {
-            return this.quote + this.value + this.quote;
+        if (!this.escaped) {
+            output.add(this.quote);
+        }
+        output.add(this.value);
+        if (!this.escaped) {
+            output.add(this.quote);
         }
     },
+    toCSS: tree.toCSS,
     eval: function (env) {
         var that = this;
         var value = this.value.replace(/`([^`]+)`/g, function (_, exp) {
diff --git a/lib/less/tree/rule.js b/lib/less/tree/rule.js
index cafe6d08..e8fe085d 100644
--- a/lib/less/tree/rule.js
+++ b/lib/less/tree/rule.js
@@ -17,24 +17,18 @@ tree.Rule.prototype = {
         this.value = visitor.visit(this.value);
     },
     genCSS: function (env, output) {
-        output.add(this.toCSS(env));
-    },
-    toCSS: function (env) {
-        if (this.variable) { return ""; }
-        else {
-            try {
-                var css = this.name + (env.compress ? ':' : ': ') +
-                   this.value.toCSS(env) +
-                   this.important + ((this.inline || (env.lastRule && env.compress)) ? "" : ";");
-                return css;
-            }
-            catch(e) {
-                e.index = this.index;
-                e.filename = this.currentFileInfo.filename;
-                throw e;
-            }
+        output.add(this.name + (env.compress ? ':' : ': '));
+        try {
+            this.value.genCSS(env, output);
         }
+        catch(e) {
+            e.index = this.index;
+            e.filename = this.currentFileInfo.filename;
+            throw e;
+        }
+        output.add(this.important + ((this.inline || (env.lastRule && env.compress)) ? "" : ";"));
     },
+    toCSS: tree.toCSS,
     eval: function (env) {
         var strictMathBypass = false;
         if (this.name === "font" && env.strictMath === false) {
diff --git a/lib/less/tree/selector.js b/lib/less/tree/selector.js
index 2a2f1cdc..1e10be14 100644
--- a/lib/less/tree/selector.js
+++ b/lib/less/tree/selector.js
@@ -55,29 +55,19 @@ tree.Selector.prototype = {
         }), evaldCondition);
     },
     genCSS: function (env, output) {
-        output.add(this.toCSS(env));
-    },
-    toCSS: function (env) {
-
-        if (!this._css) {
-            //surprised this caching works since the first element combinator is changed from ' ' to ''
-            //in the toCSS visitor, when toCSS may have already been called?
-            //is this caching worth it?
-            this._css = this.elements.map(function (e) {
-                if (typeof(e) === 'string') {
-                    return ' ' + e.trim();
-                } else {
-                    return e.toCSS(env);
-                }
-            }).join('');
-        }
-
+        var i, element;
         if ((!env || !env.firstSelector) && this.elements[0].combinator.value === "") {
-            return ' ' + this._css;
+            output.add(' ');
+        }
+        if (!this._css) {
+            //TODO caching? speed comparison?
+            for(i = 0; i < this.elements.length; i++) {
+                element = this.elements[i];
+                element.genCSS(env, output);
+            }
         }
-
-        return this._css;
     },
+    toCSS: tree.toCSS,
     markReferenced: function () {
         this.isReferenced = true;
     },
diff --git a/lib/less/tree/unicode-descriptor.js b/lib/less/tree/unicode-descriptor.js
index aa465686..7bf98ea5 100644
--- a/lib/less/tree/unicode-descriptor.js
+++ b/lib/less/tree/unicode-descriptor.js
@@ -6,11 +6,9 @@ tree.UnicodeDescriptor = function (value) {
 tree.UnicodeDescriptor.prototype = {
     type: "UnicodeDescriptor",
     genCSS: function (env, output) {
-        output.add(this.toCSS(env));
-    },
-    toCSS: function (env) {
-        return this.value;
+        output.add(this.value);
     },
+    toCSS: tree.toCSS,
     eval: function () { return this; }
 };
 
diff --git a/lib/less/tree/url.js b/lib/less/tree/url.js
index c8b72059..b2b91e8b 100644
--- a/lib/less/tree/url.js
+++ b/lib/less/tree/url.js
@@ -10,11 +10,11 @@ tree.URL.prototype = {
         this.value = visitor.visit(this.value);
     },
     genCSS: function (env, output) {
-        output.add(this.toCSS(env));
-    },
-    toCSS: function () {
-        return "url(" + this.value.toCSS() + ")";
+        output.add("url(");
+        this.value.genCSS(env, output)
+        output.add(")");
     },
+    toCSS: tree.toCSS,
     eval: function (ctx) {
         var val = this.value.eval(ctx), rootpath;
 
diff --git a/lib/less/tree/value.js b/lib/less/tree/value.js
index 2deebb57..7f110f65 100644
--- a/lib/less/tree/value.js
+++ b/lib/less/tree/value.js
@@ -18,13 +18,15 @@ tree.Value.prototype = {
         }
     },
     genCSS: function (env, output) {
-        output.add(this.toCSS(env));
+        var i;
+        for(i = 0; i < this.value.length; i++) {
+            this.value[i].genCSS(env, output);
+            if (i+1 < this.value.length) {
+                output.add(env.compress ? ',' : ', ');
+            }
+        }
     },
-    toCSS: function (env) {
-        return this.value.map(function (e) {
-            return e.toCSS(env);
-        }).join(env.compress ? ',' : ', ');
-    }
+    toCSS: tree.toCSS
 };
 
 })(require('../tree'));