Morphological descriptions, chromosome numbers, and meiotic behaviour are presented for nine different hybrids ofCarexin sectionsCryptocarpaeandPhacocystisfrom northeastern North America, mainly salt-marsh species from the St. Lawrence estuary and gulf. They areC.aquatilis×subspathacea(2n = 79),C.nigra×subspathacea(2n = 81, 83),C.nigra×salina(2n = 80),C.paleacea×salina(2n = ca. 74, 75),C.aquatilis×recta(2n = 74),C.nigra×recta(2n = 78, 79),C.paleacea×recta(2n = 73),C.aquatilis×paleacea(2n = 74), andC.nigra×paleacea(2n = 78 + fragment, 79). Hybrids showed a mixture of morphological characters from both putative parent species, and chromosome numbers were mostly intermediate between those of their parents. Meiosis of hybrids was disturbed with variable numbers of univalents, trivalents, and quadrivalents, such as in two of the parent species,C.salinaandC.recta. In general, hybrids differed from parent species by the frequent occurrence of desynaptic bivalents and higher numbers of trivalents. Pollen stainability was low in hybrids (10.0–56.6%, with two exceptionally high values of 71.8 and 92.2%). Pollen stainability was also low though quite variable inC.salina(23.7–62.8%) andC.recta(16.2–80.7%), but it was much higher inC.paleacea(92.7–100%),C.nigra(63.1–92.9%), andC.aquatilis(78.0–97.2%). Almost all hybrids and parents produced some well-formed achenes. A formula indicating the maximum affinity pairing (MAP formula) and two euploidy indexes were used to compare hybrid individuals and their parent species.Carex salinaandC.rectaare cytologically considered of hybrid origin, but they behave ecologically as stable species.