Phoradendron

Content

Description

Leafy parasitic shrubs; nodes often with inconspicuous constriction; internodes terete or angled. Leaves entire, petiolate or sessile, venation pinnate to palmate. Base of lateral vegetative branches with one or more pairs of fused, basal cataphylls, some species with one or more pairs of intercalary cataphylls separating successive pairs of foliage leaves; cataphylls in most species sterile; branching mostly percurrent, sometimes dichotomous by means of terminal inflorescences or abortion of apex. Inflorescences spike-like; peduncle simple or with several squamate, sterile internodes, followed by one to several fertile internodes; each fertile bract with 2 or 3 longitudinal series of flowers, produced basipetally by intercalary action, number of flowers variable but flower area always topped by a single median flower. Flowers small, sessile and often sunken in small axial cavities, 3-(4-)merous, occurring in diverse monoecious or dioecious patterns. Anthers sessile, 2-locular, minute. Fruit a berry, smooth to warty, mostly white, yellowish or red, perianth segments of female flower persistent, closed, erect, or spreading; seed with copious bright green endosperm and small, dicotylous embryo. (x = 14).

Distribution

C America present, Guianas present, Northern America, Southern America: Bolivia (Bolivia present); Peru (Peru present), north-central Argentina present, southern U.S.A present

A neotropical genus with at least 234 species; the geographical range is very large, reaching from southern U.S.A, Mexico, through C America and the Caribbean to Peru, Bolivia, and north-central Argentina; in the Guianas 27 species.

Chromosomes

(x = 14).1

1. 008

Notes

Phoradendron is an extremely challenging genus, partly because of innumerable uncritical species descriptions in the past, and partly because of inherent complexities. The genus is often decidedly difficult to separate from the closely related genus Dendrophthora, a separation based largely on the latter's 1-locular anther vs. 2-locular in Phoradendron. The anther is extremely small and this criterion makes it technically impossible to place novelties which lack male flowers. A second difficulty is the large number of species of Phoradendron.
Flower seriation is especially important in the genus, and is usually quite constant. However, there are cases where a great deal of caution is needed in interpretation. This is especially so in those cases where some or all fertile internodes have only 3 flowers per fertile bract (1 apical flower and 2 representing lateral series). This pattern is found in P. mucronatum, for example, and there is no way to tell whether, if more flowers had been present, the median series would be represented or not (in other words, whether the inflorescence is 3-seriate or 2-seriate, respectively). In other cases, as in P. obtusissimum, we may encounter some fertile internodes with both 3 (or even 1) and more than 3 flowers per bract; in such cases, we are able to discover the seriation type by inspecting the largest fertile internodes. Occasionally there is a great deal of sexual dimorphism, complicating the construction of keys. The key which follows is based on ascertaining the seriation type wherever possible.