30 



L. HILLIS-COLINVAUX 



Denmark, who worked in the Danish West Indies and pubHshed 

 extensively on the algae of the Canary Islands and Mauritius. Both 

 adopted Barton's fused filament characteristic for separating species, 

 and Howe added other characters which subsequently proved as useful. 

 While examining a certain abundant and distinctive West Indian plant, 

 he noticed, for example, that its secondary utricles were more than 

 twice as broad as those of most other specimens (Fig. 20, No. 11). 

 Furthermore, the character was consistent. It could be used, therefore, 

 to distinguish species, and Howe reasoned that specimens with this 

 character should have separate status and not be considered synony- 

 mous with H. tuna as Barton had done. Howe (1907), therefore, re- 

 established the species discoidea, which brought the total of accepted 

 Halimeda species to eight. 



Table II. Use of the Microscopic Chabacter of Average Diameter of 



PERiPHERAii Utricles (surface view) by Howe (1907) to Separate Halimeda 



Species with the Same Type of Nodal Filament Pattern 



Peripheral utricles, average diameter 

 < 80 [im 



Peripheral utricles, average 

 diameter > 80 \xm 



Peripheral utricles, 

 average diameter 

 49-77 [xm 



Peripheral utricles, 

 average diameter 

 30-44 [xm 



tridens 



( = incrassata) 



Predominant 

 segment shape 

 Subterete Discoid 

 monile simulans 



favulosa 



Among the microscopic characteristics investigated by Barton were 

 those of appearance and size of the peripheral utricles in surface view. 

 She did not find them particularly helpful, however, which in retrospect 

 is reasonable because her species concept was exceedingly broad. 

 Howe observed, though, that average diameters of the peripheral 

 utricles in surface view could be used to separate entities with the same 

 basic type of filament fusion at the nodes. Using the characters of 

 average diameter of peripheral utricles (surface view) and predominant 

 shape of segments (Table II), he re-established the species monile, 

 which had been placed in synonymy under incrassata by Barton, and 

 recognized a new species, simulans, which possessed the same type of 

 nodal character as the other two species (Howe, 1907). 



