THE MARINE ALG.E OF NEW ENGLAND. 31 



the genus Dolichospermum of Thwaites. Ealfs, in Annals and Mag. of Nat. History, 

 Vol. V, 2d series (1850), p. 325, following C. A. Agardh, who first described the genus 

 $l>licei-ozyga (Flora, 1827), says that in Sphcerozyga the spores are first formed from the 

 cells nearest the vesicular cells (heterocysts), as is shown by Professor Wood's figure, 

 PI. 3, Fig. 3, to be the case with the species from Camden. Neither can we regard 

 S. Carmichaelii, Harv., as a synonym of Cylindrospcrmum polysporum, Kiitz;., as given 

 by Professor Wood. Although we have examined a large number of specimens, in 

 only one instance have we found more than a single spore on each side of the het- 

 erocyst, which is quite differentfrom C. polysporum, Kiitz. 



NODULABIA, Mertens. 

 (From modulus, a little joint.) 



Filaments free, trichoma inclosed in a definite sheath, cells discoidal. 

 Heterocysts at regular intervals. Spores numerous, contiguous, not adja- 

 cent to the heterocysts. 



The genus Spermosira of Kiitzing is included under the above. 



N. Habveyana, Thuret, Class, des Nostoch. [Spermosira Harvey ana, 

 Thwaites, Phyc. Brit., PI. 173 c.) 



Filaments curved, cells discoidal, .0015-20 x .004 mm , heterocysts 

 .OOSo 111111 in diameter, spores numerous, about 4-8 together, spherical, 

 .005-70 mm in diameter. 



Charles Eiver, Cambridge, Mass. ; Europe. 



Found in small quantities, mixed with Sphcerozyga, in company with Rhizoclonium. 



SPIEULESTA, Turpin. 



(From spirula, a small spiral.) 



Filaments simple, without a proper sheath, oscillating, spirally 

 twisted. Spores unknown. 



S. tenuissima, Kiitz., Phyc. Brit., PI. 105, Fig. 3; Farlow, List of 

 Marine Alg£e, 1876. PL I, Fig. 4. 



Filaments intricately interlaced, ,0035 mm in diameter, hyaline, spiral, 

 closely twisted, cell divisions scarcely visible, oscillations rapid. 



Eastport, Maine; Gloucester, Cambridge, Wood's Holh Mass.; Europe. 



This species is common at Eastport, where it forms, mixed with species of Oscil- 

 laria, dark purple-colored patches on the wharves at low-water mark, and it is with- 

 out doubt to be found in similar localities along the whole coast. 



We found at Wood's Holl, in 1876, a species of Spirulina which formed a greenish 

 film on decaying algse five or six feet below low-water mark, and the same species was 

 collected by Mr. F. W. Hooper at Key West. It agrees closely with S. Thuretii, Crn., 

 a species which differs from S. tenuissima, Kiitz., in having slightly smaller filaments, 

 which are also less tightly coiled. It hardly seems to us, however, as though the 

 difference was sufficient to separate the two species. A Spirulina with much finer 

 filaments than in 8. tenuissima, and with. a much more open spiral, occurs at Wood's 

 Holl, but we have never found h in sufficient quantity to ascertain 4he species. 



