THE MARINE ALG.E OF NEW ENGLAND. 79 



A genus of minute algpe which form small brown spots on other plants. The speciea 

 are ubiquitous, but the specific characters are not well defined, and a good share of the 

 described species are merely different forms of the very common M. vulyare. The two 

 different kinds of sporangia are sometimes found together, but are usually on different 

 plants. Tbe genus is most nearly related to Balfsia, which may be said to be a Myri- 

 onema in which the borizontal layer has become much thickened, and the vertical fila- 

 ments, with the interspersed sporangia, instead of covering the surface uniformly, have 

 been confined to certain circumscribed portions. The two genera are closely con- 

 nected by Balfsia clavata, Cm., which was first described as a Myrionema by Carmichael. 

 In Balfsia the vertical filaments must be considered to be paraphyses, and perhaps 

 those of Myrionema should also be so considered. 



M. vulgake, Thur. (If. strangulans, Grev.; Phyc. Brit., PI. 280. — 

 If. panetiforme, Harv., Phyc. Brit., PL 41 b. — M. macuUforme, Kiitz., 

 Tab. Phyc, Vol. VII, PI. 93, Fig. 2.) 



Fronds .04-S mm in thickness, vertical filaments (paraphyses) slightly 

 club-shaped and moniliform, unilocular sporangia oval, .019-27 mm broad 

 by .03-4 mm long, sessile or borne on short pedicels. 



Everywhere common on various algse. 



In Le Jolis's Liste des Algues Marines de Cherbourg, Thuret is quoted as authority 

 for uniting several of the species of Myrionema of Harvey and Kiitzing. The alleged 

 h| ii •li fie distinctions are plainly nothing but modifications of the same species, dependent 

 on the place of growth. When found on small cylindrical frouds, as in some Entero- 

 morphce, the Myrionema surrounds the frond and constitutes the M. strangulans of Greville, 

 and when growing on flat surfaces the form known as M. punctiforme is found. In 

 this country the unilocular sporangia are very common, but we have never seen the 

 plurilocular sporangia, while in the next species the plurilocular sporangia are more 

 numerous, although both kinds are found. 



M. Leclancherii, (Chauv.) Harv., Phyc. Brit., PI. 41 a. PI. 6, Fig. 5. 



Fronds .06-10 mm in thickness, vertical filaments (paraphyses) cylin- 

 drical, unilocular sporangia oval, plurilocular sporangia .008-10 mm broad 

 by .023-30 ram long, ovate, oblong, sessile or on very short pedicels. 



On Rhodymenia pahnata. 



Gay Head, Mass. ; Europe. 



This species forms rather larger spots than the last on the common dulse. That it 

 is really distinct from M. vulgare admits of doubt. There appears to be a difference 

 in the paraphyses of the two, but such differences cannot be considered of much value. 

 We have found both unilocular and plurilocular sporangia in the present species, 

 but unfortunately have not preserved measurements of the latter. The plurilocular 

 sporangia are sometimes very numerous and stand side by side without intervening 

 paraxihyses. 



Family LEATHESIE^. 



Fronds lubricous or gelatinous, indefinitely expanded or irregularly 

 globose, consisting of a basal portion, composed of irregularly branch- 

 ing filaments formed of large, colorless cells, and a cortical portion of 

 closely packed, short, colored filaments ; paraphyses often present j 



