THE GREKN ALGAE OF NORTH AMERICA 389 



form and undivided ; an extreme much beyond anything in C. 

 elongation ; for ordinary forms the difference in size of utricles 

 is sufficient distinction. 



9. C. MUCRONATUM J. G. Agardh, 1886, p. 43. Frond 

 cylindrical, more or less regularly dichotomously fastigiate, sur- 

 face more or less roughish ; utricles cylindric-clavate, 5-10 

 diam. long, terminating in a distinct mucro. 



As described by Agardh, this species is divided between three 

 varieties, with no definite typical form ; it seems to take a place 

 in the Pacific the same as that occupied by C. tomcntositm in the 

 Atlantic, and it is probable that most, if not all reports of the 

 latter from the Pacific, really refer to this species. 



Var. CALIFORNICUM J. G. Agardh, 1886, p. 44, PI. I, fig. 3; 

 P. B.-A., No. 229. Utricles in younger parts of the frond 

 cylindrical, ending in a very acute mucro ; in the older parts 

 clavate, with a blunter mucro. Fig. 144. Alaska to Mexico. 



Var. NOVAE ZELANDIAE J. G. Agardh, 1886, p. 44. Utricles 

 in younger parts subcylindrical, with a short mucro ; in older 

 parts clavate, mucro wanting or very inconspicuous. Van- 

 couver. N. Zealand. 



In var. californiann the mucronate utricles are so well devel- 

 oped that the surface of the frond appears, even to the naked 

 eye, not so smooth as that of C. tomcntosidn. In var. novae 

 zclandiac they are much less noticeable, and some care is re- 

 cp:iired to distinguish this variety from C. tomentosum. 



2. AVRAINVILLEA Decaisne, 1842, p. IDS. 



Fronds not calcified, sessile or stipitate, coarse, greenish, 

 brownish or blackish, composed of inarticulate, cylindrical or 

 moniliform, dichotomous, interwoven filaments, terminating 

 above in a somewhat flabelliform expansion or in digitate lobes, 

 below in a mass of rhizoids or a rhizome ; chromatophores mi- 

 nute, rounded or fusiform, usually with a pyrenoid ; reproduc- 

 tion by aplanospores (?) formed in small number in sporangia 

 terminal on short branches projecting from the surface. 



A tropical genus of coarse, unsightly algae, growing abun- 

 dantly in muddy shallow water, but extending also to consider- 

 able depths. 



KEV TO THR SPECIES OF AVRAIN-VILLEA. 



i. Upper part a distinct flabellutn. 2. 



i. Upper part digitately lobed. i. A.Raivsoni. 



