  Connection of the Four Color Theorem (FCT) with some operations on trees is
described. L.H. Kauffman's theorem about FCT and vector cross product is
discussed. Operation of transplantation on trees linked with the move of
brackets according to the associative law is used to formulate a conjecture.
When map is represented as a tying of the trees this conjecture proposes the
existence of special coloring of this map. This coloring makes possible
successive transplantations such that one of these trees is transformed to
another, and all the intermediate maps are colored properly. It means (in terms
of L.H. Kauffman) that not only for two different positions of brackets in a
product of n factors the associative law works (on special values of factors)
but also there is a way of moving brackets that for all intermediate
positioning of brackets the associative law is obeyed. Some classes of trees
for which the conjecture is proved are presented.
