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Morphological descriptions, chromosome numbers, and meiotic behaviour are presented for nine different hybrids of Carex in sections Cryptocarpae and Phacocystis from northeastern North America, mainly salt-marsh species from the St. Lawrence estuary and gulf. They are C. 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), and C. 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. salina and C. 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 in C. salina (23.7–62.8%) and C. recta (16.2–80.7%), but it was much higher in C. paleacea (92.7–100%), C. nigra (63.1–92.9%), and C. 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 salina and C. recta are cytologically considered of hybrid origin, but they behave ecologically as stable species.

PIERRE MORISSETDt;pai-ternenr (Ie bioiogie, Fuc-ultl rles s c i~t z c~s 6.r de gciarie, Ulliversitk Luval. QuPbec~, G l K 7P4Cytornisis occurred regularly in pollen mother cells (PMCs) of Onor~is spa'raosa L., 0 . repens L. and 0 . a r v~n s i s L., from early meiotic prophase to telophase 11. Usually only a fevr PMCs were affected in any anther. but occasionally whole anthers showed cyromicaic patterns. Cytomixis ger~erally was found at extremities but rarely in the median parts of anthers. Since it appeared to lead to the degelaeration of affected PMCs or young rnicrospores, at. therefore, could not give rise to aneuploidy. Cytomisis is interpreted as a pathological abnormality induced by pressure building up within the developing flomer bud; it occurred where anthers pressed strongly against each other due to coilapetition for space. It is suggested that uncoordinated grc~wth rates of anthers and floral envelopes could account for intense cytomixis described in hybrids by various authors.On rencontre rbgulikrement le phCnornkne de cytomixie entre ie debut de la prophase nsbiotique et la tilophase H I dans les cellules-meres du pollen d' Clnnnis spinosa L., 63. repens L. et 0 . carvet~sis L. La plupart du temps. seules quelques cellules par anthere sont atreintes mais, dans certains cas, des phenomknes cytornictiques se rencontrent dans toute l'anthkrc. La cytomixie esb gka16ralement prksente aux extrkmitks des antheres et rarenment dans la partie mkcfiane. Ii setnble que ce ph6nomkne provoyue toujours la dkg6ntrescence des cellules afkctkes c~u des jeunes microspores et qu'il ne puisse donc conduire i la formation de gamttes aneuploi'cles. La cytomixis est considCr6e comme un symptcime parhologique prodelit par ia pression qui se devcioppe a l'intkrieur d'un bouton floral; cette interprktation s'appuie sur Ie fait que la cytomixie se renconrre Ih oil les antheres sont fortemernt appuykes Hes unes contre les autrcs B la suite d'une compkrition pour I'espace. Un taiax de croissancc non coordonn6 cles anthkres et des enveloppes florales expliquerait la cytornixie intense que pl~isieurs auteurs nnt d0critr chez des hybrides.

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