i92o] SetchcU-Gardner: Melanophyceae 587 



(1917, pp. 829-831) annoimced tlie discovery of a reduced, practically 

 microscopic gametophyte, filamentous like a dwarfed Ectacarpiis with 

 plurilocular gametangia giving rise to motile gametes Avhich either 

 fuse or develop parthenogenetically. Such a gametophyte is inter- 

 mediate between the reduced, yet still macroscopic, gametophyte in 

 some of the Asperococcaceae, and the very much modified gameto- 

 phyte of the Laminariaceae. Besides the Dictyosiphonaceae, it may 

 be desirable also to include in the Dictyosiphonales, the family of the 

 Spermatochnaceae, at least as limited to species with growth from a 

 single apical cell, in which ease our diagnosis of the order must 

 necessarily be modified. 



FAMILY 18. DICTYOSIPHONACEAE detoni 

 Characters of the order 



De-Toni, Syst. Uebers. Fucoid., 1891, p. 179 ; Syll. Alg., vol. 3, 1895, 

 p. 4-18 ; Kjellman, m Engler and Prantl, Die natiirl. Pflanzenfam., 

 1 Th., 2 Abt., 1893, p. 212. Dictyosiphoneae Kuetzing, Sp. Alg., 1849, 

 p. 484; Thuret, in Le Jolis, Liste alg. mar. Cherb., 1863, p. 72 (all 

 in part). 



We have restricted the Dictyosiphonaceae to the species of Dictyo- 

 siphon in the broader sense as including Coilanema Aresch. The genera 

 Gohia and Scytothamnus seem to us to be more properly assigned to 

 the Chordariales, since the growth in length is subapical rather than 

 strictly terminal. The resemblances between the Dictyosiphonaceae 

 and the Spermatochnaceae consist in having growth in length from 

 an apical cell and producing only zoosporangia on macroscopic plants. 

 The genus Dictyosiphon is readily recognized and delimited, but with 

 the species, it is otherwise. We have restudied the specimens from 

 our coast and arranged them as best we may. 



39. Dictyosiphon Grev. 



Fronds attached by a small parenchymatous disk, terete, filiform, 

 with several orders of branches arising alternately from all sides, 

 solid or at times fistulose, growing from an apical cell, composed of 

 two tissues, a central core of longitudinally elongated, colorless cells, 

 surrounded by a tissue of small, more or less polygonal, color bearing 

 cells ; reproduction by zoosporangia embedded in the cortical tissue ; 

 colorless hairs abundant. 



Greville, Alg. Brit., 1830, p. 55. 



