diff --git a/src/tree.c b/src/tree.c
new file mode 100644
index 0000000000000000000000000000000000000000..2317823a6aec3c0e03e799602e42436973c267aa
--- /dev/null
+++ b/src/tree.c
@@ -0,0 +1,47 @@
+/** @file tree.c
+ *  @brief Functions to handle tree structures.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "species.h"
+
+#include "tree.h"
+
+/** @brief Allocates new memory for a leaf and gives it the corresponding
+ * values.
+ */
+leaf_t*
+leaf_new_a (leaf_t *parent, leaf_t *next, leaf_t *first_child, void *data)
+{
+  leaf_t *leaf;
+
+  debug (2, "leaf_new_a\n");
+
+  leaf = (leaf_t*) xmalloc (sizeof(leaf_t));
+
+  leaf->parent = parent;
+  leaf->next = next;
+  leaf->first_child = first_child;
+  leaf->data = data;
+
+  return leaf;
+}
+
+/** @brief Creates a new child of @a parent with the given @a data. */
+leaf_t*
+leaf_new_child_a (leaf_t *parent, void *data)
+{
+  leaf_t *leaf;
+
+  debug (2, "leaf_new_child_a\n");
+
+  leaf = leaf_new_a (parent, parent->first_child, NULL, data);
+
+  parent->first_child = leaf;
+
+  leaf->level = parent->level + 1;
+
+  return leaf;
+}