New or little known epiphyllous liverworts, XII. Archilejeunea helenae Pócs &Gyarmati, sp. nova Tamás PÓCS & Andrea SASS-GYARMATI * Research Group for Bryology of the Hungarian Academy of Sciences at the Botany Department of Eszterházy College,Eger , PB. 43,H-3301, Hungary (Received 2 April 2004, accepted 15 October 2005) Abstract – A new species of Archilejeunea is described from the Mananara North Biosphere Reserve of Northeast-Madagascar. Archilejeunea helenae is distinguished from the related A. alata Steph. by its broad and short winged perianth keels ,by its very regular pinnate branching, always well developed leaf lobuli and by its overall larger cell size. Archilejeunea / Lejeuneaceae / Jungermanniopsida / Madagascar Résumé – Une nouvelle espèce de l’Archilejeunea est écrit de laRéserve de Biosphère MananaraNord de la partie nord-oriental de Madagascar. Archilejeunea helenae se dis- tingue de l’espèce voisine A. alata Steph. parses carènes de périanthe larges et courtes , par sa ramification très regulièrement pinnate, par les lobules des feuilles toujours bien développées et surtout par ses plus grandes cellules . Archilejeunea / Lejeuneaceae / Jungermanniopsida / Madagascar INTRODUCTION Archilejeunea,although the genus badly needs a thorought revision, seems to be a group of liverworts , which, during its evolution, produced a number of endemic species , which are restricted to relatively small distribution areas and only a few of the species are widespread. Madagascar, together with the other East Africanislands , has 5 known species of Archilejeunea (Grolle, 1995), while Sub- Saharan Africa has 7 of them (Wigginton et al., 1996). All,but one are endemic for the concerned area, only A.mauritiana Lindenb.occurs in both. Our new species is related closest to Archilejeuneaalata Steph., whichis relatively widespread in the East African Islands ,being knownfrom Madagascar, the Comoro Islands and from Mauritius .(Grolle, 1995). Although the characters given in the protologue of A. alata seemed to us adequate to distinguish Archilejeunea helenae at the species level, wehaveexamined the type specimen of Archilejeuneaalata (coll. Marie nr.4 Mayotte Island,Comoro,G.) The compari- son proved our assumption that they are well distinct. Cryptogamie,Bryologie, 2006, 27 (1): 103-109 © 2006 Adac. T ous droits réservés *Correspondence and reprints: lopho@freemail.hu