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XXXII. — Note on Ectocarpus. By John Rattray, M.A., B.Sc, Scottish 

 Marine Station, Granton, Edinburgh. Communicated by John Murray, 

 Esq., Ph.D. (Plates CXLVIL, CXLVIII.) 



(Read 2nd February 1885.) 



The group of the Phoeosporese was first recognised by Thuret * in 1850. It 

 includes algre that vary greatly in size, habit, external appearance, and mode of 

 branching, some possessing a flat thalloicl appearance with or without a long 

 stalk (e.g., Laminarice), others being filamentous and much branched (e.g., Ecto- 

 carpus, Sphacelaria, Chordaria, &c). The great majority of the genera 

 included in the group are marine or brackish water forms, but recently E. 

 Flahault t has described, under the name of Lithoderma fontanvm, a fresh 

 water species from the neighbourhood of Montpellier. 



All the forms included under the genus Ectocarpus are filamentous, and 

 usually much branched, E. crinitus being one of the simplest types, and E. 

 siliculosus one of the most complex. The primary branches again may be 

 straight or present gentle undulations (e.g., E. siliculosus), or may exhibit well- 

 marked geniculations at the points of origin of the ramuli (e.g., E. distortus and 

 E. Landsburgii). In some the central filament is of greater diameter than the 

 secondary branches, and so remains a prominent feature in the plant, but in 

 others this occurs to a much less degree, both being of approximately equal size 

 (e.g., E. crinitus, &c). 



The particular zone in which the Ectocarpi flourish is that extending from 

 high to low water mark, some being found over the whole bathymetrical extent 

 of this belt (e.g., E. brachiatus, E. tomentosus, E. littoralis, E. silicidosus, E. sphcero- 

 phorus), others occurring chiefly at the level of half tide (e.g.,E. crinitus), while 

 yet others are especially obtained near that of low water (e.g., E. fasciculatus). 

 Their mode of attachment, too, varies very greatly. They are to be found 

 adhering to mud-covered rocks and stones in the shade (e.g., E. crinitus) or in 

 exposed situations (e.g., E. littoralis), as well as epiphytically on other algse in 

 shaded pools (e.g., E. brachiatus), or in open places (e.g., E. sphwrophorus). 



The great majority of the species of this genus are found to grow epiphyti- 

 cally on other seaweeds, some being apparently confined to a limited number 

 of host plants, others being less restricted in this respect. Thus E. brachiatus is 

 only found associated with Rliodymenia palmata, just as Polysiphonia fastigiata 

 almost exclusively occurs on Ascophyllum nodosum, while E. fascicidatus and E. 



* Thuret, "Becherches sur les zoospores des Algues," Arm. des Sci. Nat., series iii. vol. xiv. 1850. 

 f Comptes Rendus, xcviii. (1884), pp. 1389-91. 



vol, xxxir. part in. 5 f 



