Some species of this section, native in Europe, are naturalized in N.-America; in most American herbaria they are named T. laevigatum Willd. or T. erythrospemum Andrzj. Whilst in Europe nearly 80 different and well distinguishable species of this section are known, only seven have been found in America. For sending material in loan to me, I am indebted to the directors of the following herbaria: Herbier Marie-Victorin, Montreal (MT); Gray Herbarium, Cambridge (GH) and that of the New England Botanical Club (NEBC); the Herbarium of the New York Botanical Garden (NY) and of the U.S. National Museum (US). In the Dutch collections of Leiden (L) and Utrecht (U) a few additions could be made; furthermore, recently, I studied several sheets of the Herbarium of Naturhistoriska Riksmuseet at Stockholm (S), most of these already revised by G. E. Haglund.