Psychotria sessilis var. angustifolia (Müll.Arg.) Steyerm.
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Authority
Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
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Family
Rubiaceae
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Scientific Name
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Type
Lectotype. Serra Tingua, Brazil, Pohl 1913.
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Discussion
Psychotria hancorniaefolia var angustifolia M.-Arg., Mart. Fl. Bras. 6(5): 356. 1881.
Psychotria hancorniaefolia var longifolia M.-Arg., Mart. Fl. Bras. 6(5): 356. 1881.
Psychotria sororopanensis Standley & Steyermark, Fieldiana Bot. 28: 605. 1953.
The Venezuelan and British Guianan collections of P. sororopanensis cannot be maintained as distinct from the complex of P. sessilis, and must be reduced to the var angustifolia of P. sessilis.
Müller-Argoviensis attempted to separate (Mart. Fl. Bras. 6(5): 354-358. 1881) a group of species including P. sessilis, P. hancorniaefolia, P. velutipes, and P. longipes by such characters as relative length of peduncle, relative length of bracteoles, pubescence of branches, comparative proportions of calyx to ovary, and degree of lobing of the outermost bracts. It has been found that no reliance can be placed on these characters in separating these taxa. Great variability occurs in the leaf shape, pubescence of vegetative parts, relative length of peduncle, and degree of lobing of the calyx. Both tetramerous and pentamerous flowers occur in species originally described as pentamerous. The lobing of the outer bracts, a character supposedly diagnostic for separating P. sessilis from related taxa (P. velutipes, P. longipes, and P. hancorniaefolia), cannot be relied upon, since all degrees of toothing from entire to shortly lobed to deeply lobed can be encountered. Moreover, the character of the subsessile heads, presumed to be diagnostic of P. sessilis, varies with respect to the relative length of the subtending peduncle: a Blanchet s n specimen from Rio Janeiro, identified as P. sessilis var genuina by M. Argoviensis, has peduncles 2-4 mm long, while a Dusen 10692 specimen, determined by Standley as P. sessilis, has peduncles 4-9 mm long. The specimen of Pohl 902, cited by M. Argoviensis under P. sessilis var genuina, has the young inflorescences sessile, but the older ones show peduncles 3-4 mm long. Moreover, the lobing of the outer bracts in material identified as P. sessilis varies from one specimen to another.
Likewise, in material labeled P. hancorniaefolia, the peduncles vary in length from subsessile, as in P. sessilis, to 13 mm long, as in Blanchet 3357, cited by Müller-Argoviensis under P. hancorniaefolia var variifolia. This Blanchet 3357 collection has some of the inflorescences sessile or only 1 mm long pedunculate, while other inflorescences on the same branch are pedunculate to 3 mm. Also in this collection the outer bracts vary from entire to somewhat lobed or toothed near the base. Thus, there appear to be no real differences to maintain P. sessilis and P. hancorniaefolia as separate taxa. Similarly, Smith and Downs (Sellowia 7: 90. 1956) have reduced P. velutipes to varietal rank under P. hancorniaefolia as a more densely pubescent-branched variation. However, there is considerable intergradation in the amount of pubescence and length of peduncle between P. sessilis and P. velutipes, and for that reason in this treatment I have reduced P. velutipes to synonymy under P. sessilis.
Although Smith & Downs retain P. longipes as a separate taxon from P. hancorniaefolia on the basis of the greater length and terete character of peduncles of P. hancorniaefolia, I have not found such a character to be reliable, since the peduncles of P. hancorniaefolia are as much ancipitally compressed as those of P. longipes, while the length of the peduncle in P. longipes varies from as little as 10-12 mm (Reitz & Klein 1675) to as much as 50 mm. However, there is a difference in leaf venation between these two taxa. In P. longipes the main secondary lateral nerves are directed at a slightly different angle and are more prominently manifest (as in P. heteroneura) than the finer intermediate or tertiary lateral vines, whereas in P. hancorniaefolia (= P. sessilis) all the secondary lateral nerves have the same or nearly the same fine texture and are more or less parallel with scarcely any indication of the lateral nerves crossing over into the tertiary venation as in P. longipes.
A collection from Serra do Espinhago, Minas Gerais, Brazil (Irwin, Maxwell & Wasshausen 20149) shows intergradation from pubescent P. sessilis var sessilis through P. sessilis var hancorniaefolia to nearly var angustifolia, all in the same collection. It would seem that the group of taxa centering around P. sessilis is best treated as involving several varieties instead of distinct species, and such a treatment has been followed in the present work.