CENTER FOR PHYCOLOGICAL DOCUMENTATION
DECEW'S GUIDE

Leathesia difformis ( Linnaeus ) Areschoug
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plurilocular and unilocular organs after Setchell and Gardner 1925 Synonyms: Leathesia nana Setchell et Gardner, L. amplissima Setchell et Gardner Illustrations: Abbott and Hollenberg 1976, p. 176, fig. 142, ( habit ), fig. 143 ( habit and x-section: unilocular sporangia ); Dammann 1930, fig. 3 ( presumed gametophyte of European plant ); Scagel 1967, p. 87, fig. 29 ( habit and x-section, sporophyte ); Setchell and Gardner 1925, pl. 40, fig. 52 ( x-section, sporophyte with plurilocular organs ), pl. 43, fig. 64 ( x-section, sporophyte with unilocular organs ), figs. 65, 66 ( x-section, sporophytes with plurilocular and unilocular organs respectively ), fig. 67 ( x-section, sporophyte with plurilocular organs ) Pacific Coast Distribution: Bering Sea ( Setchell and Gardner 1925, p. 512 ) to Monterey Peninsula, California ( Smith 1944, p. 115 ); San Luis Obispo Co ., California ( San Simeon; Cayucos: Sparling 1971, p. 236; Islay Creek: Silva in UC ); Santa Barbara Co ., California ( Goleta: Silva in UC; Carpenteria: Dawson 1958, p. 65 ); Channel Is ., California ( Santa Rosa I ., Anacapa I ., and San Clemente I.: Silva in UC; Santa Cruz I.: Apt et al. 1988, p. 42; Santa Catalina I.: Dawson 1954 a, p. 325 ); Dana Point, Orange Co ., California ( Dawson 1959 b, p. 186 ) to Bahia Asuncion, Baja Calif. ( Dawson 1953 b, p. 115 ) Taxonomy: Webber 1981; Novaczek 1987: ( both articles suggest that L. nana is a synonym of L. difformis ) Molecular Taxonomy: Tan and Druehl 1994; Bhattacharya, Stickel et al. 1991 Life History: plants from Sweden and France bore unilocular organs exclusively when they were young ( small ), and plurilocular organs exclusively when they were old ( large ). Isolates started with zooids from plurilocular organs grew into branched filamentous creeping systems. No copulation was observed. The creeping systems took two paths: 1 ) they formed assimilatory filaments and thus small cushions with plurilocular organs, thought to represent small Leathesias, 2 ) they formed uniseriate plurilocular organs directly on the creeping system. Sauvageau ( 1925 ) equated the creeping system with Myrionema , and took it through 6 generations of plurilocular plants. ( Kylin 1933; Sauvageau 1925 ) Phenology: spring, summer, fall annuals, appearing and reproducing sooner in the south than north Biology/Ecology: Oates 1989; Stewart 1989, p. 440; L & uuml; ning and Freshwater 1988, p. 312; D ' Antonio 1986 b, p. 269; D ' Antonio 1985, p. 204; Sousa 1984, p. 1923; Chapman and Goudey 1983; Turner 1983 a, p. 59; Druehl and Green 1982, p. 167; Stewart 1982, p. 53; Webber 1981; R. Lee 1965 a, p. 21; R. Lee 1965 b, p. 119; Widdowson 1965 b, p. 1427; Scagel 1961, p. 528; Stephenson and Stephenson 1961 b, p. 228; Rigg and Miller 1949; Doty 1946, p. 323 Ultrastructure: Cole et al. 1968; Cole and Lin 1969 Physiology: R. Schmid et al. 1994 Chemistry: Ragan and Glombitza 1986; R & ouml; nnerstrand 1943, p. 48

							J	F	M	A	M	J	J	A	S	O	N	D
BRITISH COLUMBIA						Pl													Common, throughout the intertidal on rocks, on Phyllospadix and Neorhodomela , in fully sheltered to fully exposed habitats. Scagel 1957, p. 77. Scagel 1973, p. 134. Hawkes et al. 1979, p. 94.
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COLUMBIA RIVER						Pl													Common, in the mid and low intertidal on Phyllospadix and Neorhodomela . Doty 1947, p. 34. Markham and Celestino 1977, p. 259.
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CAPE ARAGO						Pl													Abundant, in the high and mid intertidal on rocks, or on Phyllospadix , Neorhodomela larix and Odonthalia floccosa . Dawson 1965 a, p. 14.
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CAPE MENDOCINO						Pl													Abundant, in the high and mid intertidal on rocks, or on Neorhodomela larix and Phyllospadix . Kjeldsen 1995, pp. 24, 25.
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POINT ARENA						Pl													Common, in the mid intertidal on rocks and on Neorhodomela and Phyllospadix in moderately to fully exposed habitats. Johansen 1966 a, p. 98. Kjeldsen 1995, pp. 24, 25.
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SAN FRANCISCO						Pl													Abundant, in the mid intertidal on rocks, on Phyllospadix and on algae. Smith 1944, p. 114.
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