diff --git a/src/experimental/note.md b/src/experimental/note.md
index 83ba64fd..27512503 100644
--- a/src/experimental/note.md
+++ b/src/experimental/note.md
@@ -25,6 +25,8 @@ new:
 
 - m_replace?
 
+- lsystem2, lsystem3, add seed param
+
 deprecated:
     rails2sections: use m_transpose
     has
diff --git a/src/turtle/_impl/_lsystem2_impl.scad b/src/turtle/_impl/_lsystem2_impl.scad
index 7c18d1a1..ca199c76 100644
--- a/src/turtle/_impl/_lsystem2_impl.scad
+++ b/src/turtle/_impl/_lsystem2_impl.scad
@@ -3,7 +3,7 @@ use <../turtle2d.scad>;
 
 function _lsystem2_join(str_lt) = _join(str_lt);
 
-function _lsystem2_derive(axiom, rules, n, rule_prs) = _derive(axiom, rules, n, rule_prs);
+function _lsystem2_derive(axiom, rules, n, rule_prs, seed) = _derive(axiom, rules, n, rule_prs, seed);
 
 function _next_stack(t, code, stack) = 
     code == "[" ? [t, each stack] :
diff --git a/src/turtle/_impl/_lsystem3_impl.scad b/src/turtle/_impl/_lsystem3_impl.scad
index ec0496b1..19108a19 100644
--- a/src/turtle/_impl/_lsystem3_impl.scad
+++ b/src/turtle/_impl/_lsystem3_impl.scad
@@ -3,7 +3,7 @@ use <../turtle3d.scad>;
 
 function _lsystem3_join(str_lt) = _join(str_lt);
 
-function _lsystem3_derive(axiom, rules, n, rule_prs) = _derive(axiom, rules, n, rule_prs);
+function _lsystem3_derive(axiom, rules, n, rule_prs, seed) = _derive(axiom, rules, n, rule_prs, seed);
 
 function _next_stack(t, code, stack) = 
     code == "[" ? [t, each stack] :
diff --git a/src/turtle/_impl/_lsystem_comm.scad b/src/turtle/_impl/_lsystem_comm.scad
index 02e83b4a..bb05558b 100644
--- a/src/turtle/_impl/_lsystem_comm.scad
+++ b/src/turtle/_impl/_lsystem_comm.scad
@@ -8,16 +8,16 @@ function _join(str_lt) =
     let(leng = len(str_lt))
     [for(i = 0, s = str_lt[0]; i < leng; i = i + 1, s = str(s, str_lt[i])) s][leng - 1];
 
-function c_or_v(c, v, rules, rules_pr, leng, i = 0) =
+function c_or_v(c, v, rules, rules_pr, leng, seed, i = 0) =
     i == leng ? c : 
     let(idx = search([v[i]], rules, num_returns_per_match=0, index_col_num = 1)[0][0])
-    rand(0, 1) <= rules_pr[idx] ? v[i] : c_or_v(c, v, rules, rules_pr, leng, i + 1);
+    rand(0, 1, seed + i) <= rules_pr[idx] ? v[i] : c_or_v(c, v, rules, rules_pr, leng, seed, i + 1);
 
-function _derive1_p(base, rules, rules_pr) = 
+function _derive1_p(base, rules, rules_pr, seed) = 
     _join([
         for(c = base) 
         let(v = [for(r = rules) if(r[0] == c) r[1]])
-        v == [] ? c : c_or_v(c, v, rules, rules_pr, len(v))
+        v == [] ? c : c_or_v(c, v, rules, rules_pr, len(v), seed)
     ]);
 
 function _derive1(base, rules) = _join([
@@ -26,9 +26,10 @@ function _derive1(base, rules) = _join([
     is_undef(v) ? c : v
 ]);
 
-function _derive(base, rules, n, rule_prs) =
+function _derive(base, rules, n, rule_prs, seed) =
     let(
-        derive = is_undef(rule_prs) ? function(base) _derive1(base, rules) : function(base) _derive1_p(base, rules, rule_prs),
+        sd = is_undef(seed) ? rand(0, 1, seed) * 1000 : seed,
+        derive = is_undef(rule_prs) ? function(base) _derive1(base, rules) : function(base) _derive1_p(base, rules, rule_prs, sd),
         bs = [
             for(i = 0, b = derive(base); i < n; i = i + 1, b = i != n ? derive(b) : undef)
             b
diff --git a/src/turtle/lsystem2.scad b/src/turtle/lsystem2.scad
index df965c5c..5a7c939d 100644
--- a/src/turtle/lsystem2.scad
+++ b/src/turtle/lsystem2.scad
@@ -11,9 +11,9 @@
 use <_impl/_lsystem2_impl.scad>;
 use <turtle2d.scad>;
 
-function lsystem2(axiom, rules, n, angle, leng = 1, heading = 0, start = [0, 0], forward_chars = "F", rule_prs) =
+function lsystem2(axiom, rules, n, angle, leng = 1, heading = 0, start = [0, 0], forward_chars = "F", rule_prs, seed) =
     let(
-        derived = _lsystem2_derive(axiom, rules, n, rule_prs),
+        derived = _lsystem2_derive(axiom, rules, n, rule_prs, seed),
         codes = forward_chars == "F" ? derived : _lsystem2_join([
             for(c = derived)
             let(idx = search(c, forward_chars))
diff --git a/src/turtle/lsystem3.scad b/src/turtle/lsystem3.scad
index 828a3e3f..2c1371d1 100644
--- a/src/turtle/lsystem3.scad
+++ b/src/turtle/lsystem3.scad
@@ -11,9 +11,9 @@
 use <_impl/_lsystem3_impl.scad>;
 use <turtle3d.scad>;
 
-function lsystem3(axiom, rules, n, angle, leng = 1, heading = 0, start = [0, 0, 0], forward_chars = "F", rule_prs) =
+function lsystem3(axiom, rules, n, angle, leng = 1, heading = 0, start = [0, 0, 0], forward_chars = "F", rule_prs, seed) =
     let(
-        derived = _lsystem3_derive(axiom, rules, n, rule_prs),
+        derived = _lsystem3_derive(axiom, rules, n, rule_prs, seed),
         codes = forward_chars == "F" ? derived : _lsystem3_join([
             for(c = derived)
             let(idx = search(c, forward_chars))