THE MAEINE ALG^E OF NEW ENGLAND. 41 



MONOSTEOMA, (Thuret) Wittrock. 

 (From /zovog, single, and G-pufia, a bed.) 

 Fronds membranaceous, consisting of a single layer of cells, which are 

 either parenchymatous or separated from one another by more or less 

 jelly. 



As defined by Tknret, Monostroma differed from Ulva in having the cells embedded 

 in jelly rather than arranged in the usual form of parenchymatous tissue. Wittrock 

 includes iu the genus all the Ulvas consisting of a single layer. In most of the species 

 the frond is at first sack-shape, but soon ruptures, the segments being composed of one 

 layer of cells. The basal cells are prolonged downwards, but they become more or 

 less circular in the upper part. 



M. pulchrum, n. sp. 



Fronds membranaceous, fasciculate, light green, lanceolate or cuneate- 

 lanceolate, attenuated at the base, margin crisped, two to twelve inches 

 long, two inches broad, substance very delicate, about .008 mm in tkick- 

 u ess, cells irregular, more or less sinuous, intercellular substance small. 



Watch Hill, Conn., Prof. Eaton; Gloucester, Mass., Mrs. Bray; Port- 

 land, Me., Mr. C. B. Fuller. Spring. 



A beautiful and apparently not uncommon spring plant of New England, dis- 

 tinguished by its outline and delicate substance. When fully grown the fronds are 

 most frequently attenuated at the base and rather obtuse at the summit. When young 

 they arc lanceolate, and seem to be always plane, never saccate, as in the next species. 

 The color is a delicate green, and the plant cannot easily be removed from the paper 

 on which it is pressed. This species has sometimes been distributed as Ulva Lima, to 

 which it bears more or less resemblance in shape. 



M. Grevillei, Wittrock. ( Ulva LacUica, Grew non Linn. ; Harv. Phyc. 

 Brit., PI. 243, and Ner. Am. Bor., Part III, p. 60. — Entcromorplia Gre- 

 villei, Thuret.) 



Frond at first saccate, then split to the base into irregular segments, 

 color light green, segments plane, unequally laciniate, frond about 

 .012 mm thick, cells angular, intercellular substance small. 



Boston Bay (Ner. Am. Bor.); Maiden, Mass., Mr. Collins; Ives 

 Point, Conn., Mr. F. W. Hall; Europe. Spring. 



A common spring species of the Atlantic shores of Europe, but apparently not so 

 common in New England. The cells of this species vary considerably, and in some 

 specimens the intercellular gelatinous substance is tolerably prominent. 



M. Blytii, (Aresch.) Wittr. ( Ulva Blytii, Aresch., Phyc. Scand., p. 

 186, PI. 10 (j.—M.Blyttie, Wittrock, Monog. Monostr., p. 49, PI. IV, Fig. 

 11.) 



Frond membranaceous, subcoriaceous, dark green, irregularly cleft, 

 margin crisped, .028-40 mm in thickness, cells angular, closely packed, 

 intercellular substance small. 



Exs.— Nordstedt & Wittrock, Alg. Scand., No. 44; Alg. Am. Bor., 

 Farlow, Anderson & Eaton, No. 98. 



