Tin: MARINE ALG.E OF NEW ENGLAND. G5 



iiitoriial portion coiisistinjLC of an axial filament fonneil of a sin;^^lo vow 



of rather lar«;e cylindrical cells, surrounded by a mass of oblon;,^ ct'Us 



sometimes mixed with smaller windini,^ cells; in the spring fronds 



covered with branchin*^ hairs, which drop otf later in the season; 



unilocular sporani^ia formed directly from the cortical cells, which do 



not underi^o any change in shape or size; growth trichothallic. 



A small ;^onaa, cousistinj? of about fifteen described species, a considerable portion 

 of which lu'.ir a close roseniblance to 1). aculeata. They are inhabitants of the colder 

 seas in both the northern and sontheru hemispheres. Our two species are very wi<lely 

 dilViised, but D. lignlatay a coniiuon species of California as well as of Enrop(», is want- 

 inj^ on our coast. The j;enus is easily distingaish«Ml from its allies by the axial fila- 

 ment and the formation of the zoospores in the unchanged sui)erficial cells. 



D. ACULEATA, Lamx., Phyc. Brit., Tl. 40; Xer. Am. Bor., Vol. I, 

 PI. 4 h. 



Fronds dark olive-brown, one to six feet long, terete below, cora- 

 l»ressed above, naked at the base; branches alternate, numerous, long 

 and virgate, lower branches longer than upper, several times pin- 

 nate, clothed in spring with hairs, which fall oif and leave alternate, 

 distichous, spine-like i)rocesses. 



Common on exposed shores below low- water mark. Throughout the 

 year. Europe. 



A coarse and homely species .as usually found ; often washed ashore in large masses. 

 Not likely to be confounded with any other of our species. In spring it presents a 

 feathery appearance, owing to the tufts of hairs with which the frond is beset. It 

 is one of the species used as a fertilizer on the northern coast of New England. 



D. viRLDis, Lam. (Dichloria viridis, Grev. — Desmarestia viridiSy 

 Phyc. Brit., PI. 312.) 



Fronds light olive, one to three feet long, cylindrical or but slightly 

 compressed; branches all opposite, distichous, several times pinnate, 

 ultimate branches capillary. 



Common on stones at and below low-water mark. Europe. 



A smaller and much more delicate species than the last, for which it can never bo 

 mistaken, rather resembling in some of its conditions a Dictyosiphoti. The name is 

 derived from the fact that on decaying or on being placed in fresh water it turns 

 quickly to verdigris-green. Harvey mentions that air-cavities are to be seen in cross- 

 sections of the filaments. The air-cavities are, however, merely the sections of tho 

 larger cells which are surrounded by dense masses of smaller cells, wherejis in I), 

 aculeata a cross-section shows the axial filament surrounded by a mass of cells of 

 nearly equal diameter. 



Family DICTYOSIPIIOXEiE. 



Fronds branching, fdiform, axis composed of elongated cuboidal cells, 

 the cortex of smaller roundish cells; unilocular sporangia spherical, 

 scattered or aggregated, formed from the subcortical cells; plurilocular 

 sporangia unknown. 



