Preliminary notes on Justicia (Acanthaceae) in Peru

<i>Justicia</i> L. is the most species-rich genus of Acanthaceae in Peru and is here accepted in its broader traditional circumscription. The present paper marks a preliminary step towards a complete revision of the genus in Peru. Taxonomic notes and full synonymy are provided for 45 species including twenty-one new species, all apparently endemic to Peru: <i>Justiciaangustituba</i> J.R.I.Wood & R.Villanueva, <i>J.baguensis</i> J.R.I.Wood & R.Villanueva, <i>J.bambusiformis</i> J.R.I.Wood & R.Villanueva, <i>J.chamaecaulis</i> J.R.I.Wood & R.Villanueva, <i>J.cajamarcensis</i> R. Villanueva & J.R.I.Wood, <i>J.discolor</i> J.R.I.Wood & R.Villanueva, <i>J.falcifolia</i> J.R.I.Wood & R.Villanueva, <i>J.huallagensis</i> R.Villanueva & J.R.I.Wood, <i>J.hyalina</i> J.R.I.Wood & R. Villanueva, <i>J.lactiflora</i> J.R.I.Wood & R.Villanueva, <i>J.longibracteata</i> J.R.I.Wood & R.Villanueva, <i>J.oppositiflora</i> R.Villanueva & J.R.I.Wood, <i>J.oxapampensis</i> R. Villanueva & J.R.I.Wood, <i>J.rojasiae</i> R.Villanueva & J,R.I.Wood, <i>J.saccata</i> R.Villanueva & J.R.I.Wood, <i>J.sagasteguii</i> J.R.I.Wood & R.Villanueva, <i>J.schunkei</i> J.R.I.Wood & R. Villanueva, <i>J.spathuliformis</i> R.Villanueva & J.R.I.Wood, <i>J.tumbesiana</i> R.Villanueva & J.R.I.Wood, <i>J.valenzuelae</i> J.R.I.Wood & R.Villanueva and <i>J.werffii</i> J.R.I.Wood & R.Villanueva. New subspecies, subsp. machupicchuensis J.R.I.Wood & R.Villanueva of J.alpina Lindau and subsp. filisepala J.R.I.Wood & R.Villanueva of <i>J.discolor</i> are described. The genus <i>Tessmanniacanthus</i> Mildbr. is united with <i>Justicia</i>, the only species in the genus, <i>T.chlamydocardioides</i> Mildbr. being treated as <i>Justiciachlamydocardioides</i> (Mildbr.) R.Villanueva & J.R.I.Wood. <i>Justicialoxensis</i> Wassh., <i>J.poeppigiana</i> (Nees) Lindau, <i>J.sessilifolia</i> (Lindau) Wassh., <i>J.soukupii</i> (Standl. & F.A. Barkley) V.A.W.Graham and <i>J.tenuistachys</i> (Rusby) Wassh. & J.R.I.Wood are treated as synonyms respectively of <i>J.chimboracensis</i> Wassh., <i>J.secundiflora</i> (Ruiz & Pav.) Vahl, <i>J.alpina</i> Lindau, <i>J.radicans</i> Vahl and <i>J.tenuiflora</i> Ruiz & Pav. Fourteen names are lectotypified. The paper is copiously illustrated with line drawings, photographs and pollen images. Distribution maps supplement the information on ecology and distribution provided for all species discussed.