66 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



DICTYOSIPHON, Grev. 



(From diKTvov, a net, and aupuv, a tube.) 

 Fronds olive-brown, filiform, branching, solid above, becoming hol- 

 low below, cortex composed of small, irregularly polygonal cells, inte- 

 rior of larger, colorless, longitudinally elongated cells ; branches corti- 

 cated throughout; growth from an apical cell (scheitel-zelle) ; unilocu- 

 lar sporangia spherical, scattered, immersed in the cortex; paraphyses 

 and plurilocular sporangia unknown. 



The genus was founded on D. fceniculaceus, a species placed by C. A. Agardh and 

 Lyngbyo in Scytosiphon. Under D. fceniculaceus were included a number of forms 

 which have since been separated by Areschoug and placed in two different genera, 

 Phlceospora and Dictyosiphon. In the former the unilocular sporangia are formed 

 directly from the cortical cells and cover the surface in dense patches, at maturity 

 projecting above the surface of the frond. In the latter genus the sporangia are scat- 

 tered and immersed. In Dictyosiphon, moreover, the growth is from an apical cell, 

 but in Phloeospora it is trichothallic, and in the former genus the superficial cells are 

 polygonal and irregularly placed, while in the latter they are quadrate and arranged 

 in regular series. The genus is divided by Areschoug into two subgenera, Dictyosi- 

 phon proper and Coilonema, the latter of which is referred by Gobi to Cladosiphon, since 

 the cortical layer consists of very short filaments rather than a continuous cellular 

 membrane. Our two species belong to Dictyosiphon proper, but species of Coilonema 

 and Phheosporn are to be expected in the region of Eastport. By Harvey the genus 

 was placed in the Dictyotacw, from which order it was necessarily removed wheu the 

 true nature of the sporangia was discovered. 



D. fgeniculaceus, Grev. (Scytosiphon fceniculaceus, Ag. — J), fceni- 

 culaceus, Phyc. Brit., PI. 326; Areschoug, Phyc. Mar., PI. 7.) 



Fronds yellowish brown, six inches to two feet long, much branched ; 

 branches alternate or occasionally opposite; superficial cells angularly 

 quadrate. 



Common on stones and algre at low- water mark. Spring and summer. 



Europe. 



A variable species as found on our coast, but one which cannot well be subdivided 

 at present. Early in the season the fronds are light colored and delicate in substance, 

 but later they become more rigid. Perhaps some of the forms which we have hero 

 included may properly be placed under var. flaccidus of Areschoug. Such, at least, 

 appears to be the case with some of the specimens collected in May at Wood's Holl. 



D. hippuroides, (Lyngb.) Aresch. ? (Scytosiphon hippuroid.es, Lyngb., 

 Hydr., PI. 14 b. — D. fceniculaceus a, Aresch., Phyc. Mar., PI. 6 a and b. — 

 Chordaria flagelliformis var. /3 and y, Agardh, Sp. Alg., Vol. I, pp. 66 

 and 67.) 



Fronds dark brown, four inches to two feet long; main branches 

 rather densely beset with flagellate, scattered, subequal secondary 

 branches; superficial cells in the lower part arranged in horizontal 

 series, above irregular. 





