Howe: Phycological studies 99 



thicker (0.4-0.6 vs. 0.O9-0. 16 mm.), more rigid, less zonate 

 flabellum and its subcuneate base, by the larger (46-84// vs, 8- 

 30 //), less flattened filaments, which are regularly and strongly 

 constricted above the dichotomies, and by the character of their 

 lateral appendages, which are closely 1-3 times dichotomous in- 

 stead of simple or once furcate and are 55-160// long instead of 

 11-30/^, long, the spines crowning a thick stump-like base or 

 pedestal instead of being practically sessile. 



From Udotea argentea Zanard., judging by the original descrip- 



w 



tion and figures, by a description recently published by A. & E. 

 S. Gepp,* and by American plants which we are somewhat doubt- 

 fully identifying with that species, U, spimilosa differs in its much 

 thicker, more rigid, less zonate flabellum, which is ^—'j- instead of 

 I- or 2-stratose, in the filaments being constricted above the dichot- 

 omies, in their spine-like instead of obtuse, truncate, or capitate 

 appendages, which are secund instead of commonly protruding in 

 all directions, and in the taper-pointed instead of truncate or 

 obtuse ultimate divisions of the stipe-cortex. 



From Udotea coiighitinata, U. spimdosa differs greatly in the 

 presence of appendages on the filaments of the flabellum and in 

 the calcareous sheaths of the filaments being non-porose. 



From Udotea Flabellum, with its strongly marked zonations and 

 highly differentiated cortex, the present species is so widely differ- 

 ent that comparison is unnecessary. 



* Trans. Linn. Soc. Bot. 11. 7 : 176, 1908. 



