Ludwigia sect. Ludwigia
erect, subterete to angled.
alternate.
4-merous;
petals present, yellow;
stamens as many as sepals;
pollen usually shed in tetrads.
globose to cuboid, 4-angled or terete, with hard walls, dehiscent by an apical pore.
in several rows per locule, free, raphe an inconspicuous, longitudinal ridge.
= 16.
Ludwigia sect. Ludwigia
Species 4 (4 in the flora).
Species of sect. Ludwigia are found mainly along the coastal plain of southeastern United States.
Section Ludwigia consists of four perennial diploid species native to the southeastern United States; L. hirtella extends north to Rhode Island and L. alternifolia to Ontario and into the Great Plains of central North America (P. A. Munz 1965). Ludwigia virgata is outcrossing, the other three are autogamous. This strongly supported monophyletic section (P. H. Raven 1963[1964]; Liu S. H. et al. 2017) differs from the other sections found in North America by having fusiform, tuberous roots that may have an adaptive function in wet habitats, and capsules regularly dehiscing by an apical pore. The free seeds are loose in the globose capsules until they dehisce through the pore, giving rise to the common names seedbox or rattlebox. All species of sect. Ludwigia consistently shed their pollen in tetrads; J. Praglowski et al. (1983) reported for all taxa in this section that sometimes the tetrads appeared to be linked, suggesting polyads.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
