We establish the algorithms and procedures that augment by trees the classfiers of binary feature vectors in (Gyllenberg et. al. 1993, 1997, Gyllenberg et. al. 1999 and Gyllenberg and Koski 2002). The notion of augmenting a classifier by a tree is due to (Chow and Liu 1968) and in a more extensive form due to (Friedman et. al. 1997). These techniques will in another report be primarily applied to unsupervised classification of bacterial DNA fingerprints (or electrophoretic patterns), c.f., (Gyllenberg and Koski 2001 (a), Rademaker et. al. 1999). By classification we mean here both the (unsupervised) procedures of finding the classes in (training) data of items as well as the actual outcome of the procedure, i.e., a partitioning of the items. By identification we mean the procedures for finding the assignment of items in classes, pre-established in one way or the other. The distinction should be clear, although the algorithms of classification as given in the sequel will also...