14 Rhodora [JANUARY 
erence or of convenience than anything else, whether the forms are 
distinguished as marked varieties or nearly allied species; the seven 
forms united by Rosenvinge are here divided into two groups, one 
included as varieties under M. Grevillei, the other as M. arcticum, 
it seems more convenient to keep apart forms such as M. angicavum 
with very thick membrane and large, vertically elongate cells, and 
the thin membraned typical M. Grevillei, with small, horizontally 
elongate cells. All the forms mentioned are found in Greenland, 
but are not recorded farther south on this coast; they occur also in 
northern Norway; the type is found in Alaska. Kjellman (1) 299. 
M. Grevillei var. arctica Rosenvinge (1) 949, fig. 51; (2) 152, fig. 51. 
M. saccodeum Kjellman (1) 296, Pl. XXVIII, figs. 1-10. M. cylindra- 
ceum Kjellman (1) 295, Pl. XXX. M. angicavum Kjellman (1) 297, 
Pl. XXIX. Exsicc, Phyc. Bor.-Am., gro, 
Var. INTESTINIFORME Rosenv. (1) 153, 1893. Frond tubular, up 
to 50 cm. long; membrane 25-50 p thick; cells rounded, closely set, 
vertically oval in cross section, 15-20 4 high; usually arranged in 
more or less distinct series longitudinally. 
This variety resembles in habit M. Grevillei var. Vahlii, but is 
more persistently tubular, and except by careful examination of its 
structure, is liable to be mistaken for Ænteromorpha intestinalis. It 
is found in Greenland. Rosenvinge (1) 953, fig. 52: (2) 153, 
fig. 52. 
4. M. PULCHRUM Farlow (4) 41, 1881; J. G. Agardh, Till Alg. 
Syst. part 3, 104, 1882; De Toni, Syll. Alg., Vol. I, 110, 1889. 
Frond dividing into linear or lanceolate segments with slender base, 
much crisped at the margin, light green, membrane about 6 p thick 
in upper part, up to 15 u near base, cells roundish, rather irregular 
in form. Plate 41, fig. 8, cross section ; fig. 9, surface. 
A beautiful species, extremely delicate, adhering so closely to paper 
when mounted that it is almost impossible to detach it for examina- 
tion, It occurs on rocky shores, usually epiphytic on other algae, 
and is found from April to June on the New England coast, where 
it occurs as far south as Newport, Rhode Island, and north to 
Newfoundland. 
Foslie and Rosenvinge include M. pulchrum under M. undulatum, 
as var. Farlowii, Foslie; but this is probably incorrect. It may be 
that specimens of the latter variety have been distributed under the 
name of M. pulchrum, as there is some external resemblance between 
them. The latter is, however, more delicate and is usually divided 
so as to resemble a tuft of fronds of Huteromorpha Linza, with nar- 
row tips, the edges much crisped and wavy; while the former has 
a generally rounded and fan-like outline, the plications long and 
radiating from the base to the margin. Both, however, vary consid- 
erably, and forms can be found which it would be hard to distinguish 
by external characters. Even if we accept the statement of J. G. 
