18 ! Rhodora 1 [January 
10. M. GROENLANDICUM J. G. Agardh, Till Alg. Syst., Part 3, 107, 
Pl III, Figs. 80-83, 1882; De Toni, Syll. Alg., Vol. I, 106, 1889. 
Frond filiform, tubular, cylindrical, up to 15 cm. long, from a very 
slender base expanding to 1 mm. diameter ; apex broken only after 
exit of zoospores. Cells in the lower part of the frond loosely arranged 
in twos and fours, roundish angular; in the upper part more evenly 
distributed, more or less closely set. In cross section the membrane 
is 25-35 p thick; the cells radiately elongate, 2-4 times as long as 
broad; in the younger parts the central cavity is filled with a gelat- 
inous substance, which disappears as the plant becomes older. 
Zoospores formed first at the summit of the frond, and developing 
successively in lower cells. Plate 41, fig. 20, cross section; fig 21, 
surface. 1 
This plant has no external resemblance to a Monostroma, and was 
placed in this genus with a mark of doubt by both Farlow and Rosen- 
vinge. It appears like a slender unbranched Jm/eromorpha, but 
seems, however, to be in structure more nearly related to Monostroma. 
It has been found at Nahant and Swampscott on the Massachusetts 
coast; at Newfoundland; at several places in Greenland and in 
Alaska. It occurs from April to June in New England; in July at — 
Newfoundland; and from May to August in Greenland. At Nahant, 
it grows in rather dense tufts, at the lower limit of the litoral zone, 
in company with Cladophora arcta, Bangia fusco-purpurea, Urospora 
penicilliformis, etc. Rosenvinge (1) 954, fig. 53; (2) 155, fig. 53; 
(3) 117. Saunders (1) 410. Collins (8) 44. Exsicc. Phyc. Bor.- - 
Am., 13. M. Collinsii Alg. Am.-Bor., 216, without description. 
ENTEROMORPHA Link. 
Frond originating in a single series of cells, which by repeated 
division form a tubular frond, the membrane of which consists of a 
single layer of cells; in some of the simpler species the tubular stage 
is not reached, and the frond in the adult state consists of two or a 
few series of cells, united without any interior open space. All the 
cells of the frond, except the lowest, capable of producing zoospores, 
which are discharged through an opening in the cell wall. 
A large genus, at least 5o species having been described, of which 
a part will probably be united with other species. It is connected 
with Uwa by Æ. Linza, in which the tube is compressed, and the 
membranes united in the median part; on the other hand, Monostroma 
Groenlandicum is hardly to be distinguished from some of the simple 
filiform species of Enteromorpha. ŒE. intestinalis is found the world 
over, and other species are very widely distributed. They are found 
not only in the sea, but also about salt springs and salt mines ; they 
abound in brackish, and are occasionally found in quite fresh water. 
