Flora Mesoamericana, Volume 2 (1), Ceratophyllaceae, page 1 of 5 First published on the Flora Mesoamericana Website, 2 Sep. 2015. 52. CERATOPHYLLACEAE By F.R. Barrie. Herbs; perennial; aquatic, submersed; monoecious; aerenchyma present in stems and leaves, glabrous throughout. Roots absent. Stems suspended or anchored to the substrate. Leaves whorled, 3-11 per node, apetiolate, estipulate; blades filiform or two to four or more times dichotomously branched, the ultimate segments linear and finely to coarsely toothed. Flowers solitary, unisexual, actinomorphic, sessile or subsessile, subtended by an involucre of 8 to 15 linear bracts, 1.5 --2 mm; calyx and corolla absent; stamens 3 to numerous, c. 2 mm, 2-locular, longitudinally dehiscent, the connective projecting apically, bearing 2 or more small teeth; ovary 1, superior, 1-locular; ovule 1, pendulous; style 1, terminal, persistent, aciculate or awl-shaped; stigma decurrent within a stylar groove. Fruit an achene, ellipsoid, moderately compressed laterally, the surface smooth to papillose or tuberculate, the margin entire or winged, with or without basal, marginal and apical spines; seed 1, elliptical, without endosperm, the embryo well developed. 1 gen., 6 spp. Cosmopolitan. Bibliography: Les, D.H. Fam. Gen. Vasc. Pl. 2: 246-250 (1993). 1. Ceratophyllum L. Dichotophyllum Moench By F.R. Barrie. Characters as for the family. Ceratophyllum is a genus of submerged aquatic herbs occurring in lakes, ponds, swamps and slow moving streams, found on all continents. It often forms dense vegetative mats. Flowers are submerged at anthesis and pollen is dispersed by water. Flora Mesoamericana, Volume 2 (1), Ceratophyllaceae, page 2 of 5 Duke (1962) suggested that C. echinatum A. Gray might possibly occur in Panama, although it had not been collected there. The distribution of that species, however, is restricted to the eastern United States and to Canada (Les, 1997). Wilmot- Dear (1985) treated C. echinatum as a variety of C. submersum L. and Carnevali et al. (2010) reported C. submersum var. echinatum (A.Gray) Wilmot-Dear from Tabasco and Campeche. Wilmot-Dear (1985) considered both C. muricatum Cham. and C. australe Griseb. to be synonyms of C. submersum var. echinatum, whereas Les (1988) considered C. muricatum to be a distinct species and C. australe to be a subspecies of it. The Tabasco specimens examined for this treatment (no Campeche specimens have been seen) are referred to C. muricatum subsp. australe (Griseb.) Les. Bibliography: Les, D.H. Syst. Bot. 11: 549-558 (1986); Syst. Bot. 13: 73-86 (1988). Lowden, R.M. Aquat. Bot. 4:127-142 (1978). 1. Leaves crowded apically; blades of larger leaves divided once or twice, rarely more; fruit margin not winged, without marginal spines. 1. C. demersum. 1. Leaves more or less uniformly distributed; blades of larger leaves divided three or four times; fruit margin winged, with 2-20 spines. 2a. C. muricatum subsp. australe. 1. Ceratophyllum demersum L., Sp. Pl. 2: 992 (1753). Lectotype (designated by Aziz, 1974): Herb. Clifford: 446, Ceratophyllum 1 (BM!). llustr.: Lowden, Aquat. Bot. 4: 129, t. 1 (1984). Ceratophyllum apiculatum Cham., C. demersum L. var. apiculatum (Cham.) Asch., Dichotophyllum demersum (L.) Moench. Stems to c. 3 m, freely branched and often forming dense mats. Leaves crowded apically, bright to dark green; blades 1--3 cm; dichotomously branched once or twice, rarely thrice in the largest leaves, rarely simple, the ultimate segments linear, the marginal teeth conspicuous, typically with a broad base. Fruit3 3.5--6 x 2--4 x 1--2.5 mm, green or reddish brown, the basal spines 2, 0.1--12 mm, rarely absent, straight or curved; marginal spines and wings absent; apical spine 0.5--14 mm. Lakes, ponds, slow-moving rivers or streams, swamps. T (Orozco S. & González 1, MO); C (Ocaña N. 72, MO); Ch Flora Mesoamericana, Volume 2 (1), Ceratophyllaceae, page 3 of 5 (Cowan 3203, CAS); G (Steyermark 4728, F); H (Carr 2351, F); ES (Fassett 28748, F); N (Moreno 21135, MO); CR (Crow & Rivera 6276, F); P (Kennedy 2375, MO). 0-1400 m. (Canada, USA, Mexico [Baja California Sur, Distrito Federal, Michoacán, Nayarit, Oaxaca, Tamaulipas, Veracruz], Mesoamerica, Colombia, Guayanas, Ecuador, Peru, Bolivia, Brazil, Argentina, Cuba, Jamaica, Hispaniola, Puerto Rico, Europe, Africa, Asia, Australia, New Guinea.) 2. Ceratophyllum muricatum Cham., Linnaea 4: 504 (1829). Lectotype (designated by Les, 1988): Egypt, Sieber s.n. (HAL; isolectotype MO!). Illustr.: Chamisso, Linnaea 4: t. 5, f. 6c (1829). Ceratophyllum demersum var. muricatum (Cham.) K. Schum., C. submersum L. subsp. muricatum (Cham.) Wilmot-Dear. Les (1988) recognized three subspecies in Ceratophyllum muricatum, two of which, subsp. muricatum and subsp. kossinskyi (Kuseneva-Prochovora) Les are restricted to Europe, Asia and Africa. The distribution of the third, subsp. australe, is exclusively New World. The fruit of subsp. australe is, on average, larger than that of the other two subspecies, but the variation in size and of spine length and number can be considerable. 2a. Ceratophyllum muricatum Cham. subsp. australe (Griseb.) Les, Syst. Bot. 13: 85 (1988). Ceratophyllum australe Griseb., Abh. Königl. Ges. Wiss. Göttingen 24: 14 (1879). Lectotype (designated by Les, 1988): Argentina, Lorentz & Hieronymus 547 (GOET, web image!). Illustr: Lowden, Aquat. Bot. 4: 132, t. 2g-k (1984). Ceratophyllum demersum L. var. cristatum K. Schum., C. floridanum Fassett, C. llerenae Fassett. Stems to c. 1 m, freely branched. Leaves more or less uniformly distributed along the branches, yellow-green; blades 1--3 cm, the larger leaves dichotomously branched 3 or 4 times, the ultimate segments linear, the marginal teeth weak and inconspicuous. Fruits 3--4.5 x 2--3 x 1--2 mm, green or dark brown; basal spines 2, straight or curved, 0.3--4.5 mm, rarely absent; margins narrowly winged, bearing 2 to 20 spines, 0.1--4 mm; apical spine 1.5--7.5 mm. Ephemeral or persistent in ponds and lakes. T (Orozco S. & González 5, MO); C (Carnevali et al. 2010: 117); B (Peck 894, NY); G (Tonduz 594, Flora Mesoamericana, Volume 2 (1), Ceratophyllaceae, page 4 of 5 GH); ES (Fassett 29116, F); N (Stevens & Montiel 27595, MO); CR (Crow & Rivera 7406, F). 0-500 m. (USA [Florida, Georgia, North Carolina], Mexico [Tamaulipas], Mesoamerica, Colombia, Venezuela, Suriname, Ecuador, Peru, Bolivia, Argentina, Brazil, West Indies.) Literature cited: Aziz, K. 1974. Ceratophyllaceae. In: Nasir, E. & S.I. Ali, eds., Fl. West Pakistan 70: 1--3. Carnevali, G., J.L. Tapia-Muñoz, R. Duno de Stefano & I.M. Ramírez Morillo. 2010. Flora ilustrada de la península de Yucatán : listado florístico . Centro de investigación científica de Yucatán. Merida, 1-326. Duke, J.A. 1962. Ceratophyllaceae. in: Woodson, R.A. & Schery, R.W., eds., Flora of Panama IV (5), Ann. Missouri Bot. Gard. 49: 144. Les, D.H. 1986. The evolution of Achene morphology in Ceratophyllum (Ceratophyllaceae) I. Fruit-spine variation and relationships of C. demersum, C. submersum and C. apiculatum. Syst. Bot. 11(4): 549-558. ----------. 1988. The evolution of achene morphology in Ceratophyllum (Ceratophyllaceae), II. Fruit variation and systematics of the “Spiny-Margined” Group. Syst. Bot. 13(1): 73--86. ----------. 1993. Ceratophyllaceae. In: Kubitzki, K., ed., The Families and Genera of Flowering Plants 2: 246-250. Springer-Verlag. Berlin. ----------- 1997. Ceratophyllaceae. In: Flora of North America Editorial Committee, eds., Flora of North America, Magnoliophyta: Magnoliidae and Hamamelidae. 3: 81-- 84. Oxford University Press, New York. Lowden, R.M. 1978. Studies on the submerged genus Ceratophyllum L. in the Neotropics. Aquat. Bot. 4: 127--142. Wilmot-Dear, M. 1985. Ceratophyllum revised – a study in fruit and leaf variation. Kew Bull. 40: 243-271. Names: Ceratophyllum apiculatum Cham. Flora Mesoamericana, Volume 2 (1), Ceratophyllaceae, page 5 of 5 Ceratophyllum australe Griseb. Ceratophyllum demersum L. Ceratophyllum demersum var. apiculatum (Cham.) Asch. Ceratophyllum demersum var. cristatum K. Schum. Ceratophyllum echinatum A. Gray Ceratophyllum floridanum Fassett Ceratophyllum llerenae Fassett Ceratophyllum muricatum Cham. Ceratophyllum muricatum subsp. australe (Griseb.) Les Ceratophyllum submersum L. Ceratophyllum submersum var. echinatum (A. Gray) Wilmot-Dear. Ceratophyllyum submersum L. subsp. muricatum (Cham.) Wilmot-Dear .