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Herbs, subshrubs, shrubs or treelets, sometimes with scrambling branches, rarely climbers or lianas. Stems usually with swollen nodes. Prophyll (a bract-like structure) present at base of axillary shoot-apex in flowering branches, minute or well developed, soon caducous; another bract-like sheathing structure is present in some species (e.g. P. hispidum). Leaves alternate; petioles often vaginate or winged, at base only or to apex (base of leaf blade), their margins may extend beyond base of blade; blades basely attached or peltate, symmetrical or asymmetrical, at base often quite some difference in attachment of blade to petiole (measures are given where this occurs), glabrous or variously pubescent, often glandular-dotted, sometimes scabrous; palmately or pinnately veined. Inflorescences simple, pedunculate spikes, solitary, leaf-opposed (in P. peltatum axillary on reduced, leafless branches, umbel-like); floral bracts peltate, rounded, triangular or cucullate, subtending reduced flowers. Flowers bisexual (in P. hymenophyllum protandrous, functionally unisexual); stamens 1-6, filaments short (long exserted in P. hymenophyllum); ovary sessile or occasionally on a short stipe, stigmas (2-)3-4, sessile or on a style. Fruits drupes, embedded in rachis to exserted, separate from each other or in compact rows, glabrous or with indument, globose or variously shaped due to compression, stigmas persistent.


Guianas: present Neotropics: present Pantropical: present
Pantropical, ca. 2000 species; in the Neotropics ca. 600 species; in the Guianas 58 species of which 11 endemics.


My findings agree with the data found in the literature, which however are scanty due to the fact that the wood is of no commercial value. In general, the wood is rather homogeneous. The main difference was found in the intervessel pitting and the vessel-parenchyma pitting which vary from alternate-confluent to scalariform. No correlation was found with other, quantitative characters like vessel diameter and number, vessel member length, or ray type.
P. bartlingianum shows the narrowest vessels and the narrowest rays.
The ideoblasts found in the rays of P. aduncum remind of Williams’ remark (1936) that the wood is sometimes fragrant.
The transverse section of P. hostmannianum is highly similar to P. poiteanum, the only climbing species studied, viz. in vessel arrangement, and in the rays, which are unlignified towards the phloem. However, differences are found in the vessel pits, those of P. poiteanum being alternate to confluent, and in the ray cells, those of P. poiteanum being square (to very slightly upright).
P. peltatum, considered long-time in the Pothomorphe genus fits nicely in Piper.


Vessels round to oval, solitary and in small multiples, diffuse, regularly distributed, diameter 30-45 μm in P. bartlingianum, to 100-150 μm in P. aduncum, often small and large vessels intermingled; number per mm2 often difficult to count because of the relatively narrow zones between the broad rays, from 5-11 in P. aduncum to 36-50 in P. poiteanum. Perforations simple. Intervascular pits oval, 5x6 μm, with anastomosing apertures (P. aduncum, P. poiteanum, and P. reticulatum) or scalariform (P. arboreum, P. bartlingianum, P. vs. crassinervium, P. hostmannianum, P. obliquum, and P. peltata). Vessel-parenchyma pits elongate to scalariform. Vessel member length 150-200 μm (P. aduncum) to more than 500 μm (P. vs. crassinervium and P. obliquum). Some wood samples show a slight tendency to storied structure due to the axial arrangement of the vessel members and parenchyma strands.
Rays very high and wide, up to ca. 15-25 cells, 200-450 μm broad (but ca. 9 cells, 100 μm in P. bartlingianum), consisting of slightly irregular, square and upright cells; in P. aduncum and in one sample of P. obliquum, islands of procumbent cells are included. Empty ideoblasts in P. aduncum. In P. hostmannianum the outer 2.5 mm is unlignified. Due to the structure of the wood, vessel-ray pits could hardly be found. The scanty pits that could be observed, were similar to the vessel-parenchyma pits.
Parenchyma paratracheal-vasicentric in narrow complete or incomplete rings; fusiform cells or 2(-4)-celled strands.
Fibres moderately thick-walled, walls 3-4 μm, lumina up to 15 μm wide, sometimes septate. Pits simple to minutely bordered, slitlike, numerous on radial walls, scanty on tangential walls.


Several authors have arranged the many species into separate genera, or in various subgeneric entities. Due to the fact that in this treatment only a relatively small area is covered, I have not gone into the trouble of assigning species to subgeneric groups. There is no general agreement on the characteristics that describe those groups. It is better to await the results of recent cladistic and phylogenetic research that will elucidate the relationships within Piperaceae and especially in Piper.
One of the characters used to define sections is the number of stamens per flower. I am convinced that this is constant, it is given in literature (Jaramillo & Manos) that this number depends on the tightness of the floral arrangement on the spike. Only if we find the same combination of character states in different parts of the plant it could be useful in a flora, especially in the key. In this treatment I have tried to use practical characters instead.
In dicotydonous plants two prophylls can be developed, but in Piper only one is developed. The place of Piper in either dicots or monocots is under study.