P. ser. Albisucca, ser. nov.
TYPE: P. albisuccus Croat
Internodia brevia; succus albus, calcareus; cataphylla persistens in fibrae tenues pallidae; petiolus subteres; lamina ovato-cordata; inflorescentia solitaria; pistilla 5-6 locularia; locules cum 18-20 seminibus.
Etymology: Albus = white; succus = juice, sap, in reference to the white sap of cut parts.
The series consists of a single species, P. albisuccus, characterized by having copious white, which turns chalky on drying. Only one other species in Central America, P. cretosum shares this unusual feature of white sap. It may belong in the same series despite its linear to oblanceolate leaf blades. It currently is placed in P. subsect. Canniphylla.