THE GRKKN AI.GAK OF NORTH AMKKICA 399 



Forma tripartita (Barton) nov. comb.; //. incnissnttt forma 

 lrif>tirtita Barton, 1901, p. 27, PI. IV, fig. 43. Lower segments 

 cylindrical; upper segments often tripartite, deeply cut, divi- 

 sions cylindrical. 



A common and variable species, of which forms with broader 

 and tridentate segments have been known as //. h ideas, those 

 with many cylindrical segments as //. iticnissata. Both forms 

 are found together in Florida and the West Indies. 



2. H. MONILK Lamouroux, 1812, p. 186 ; P. B.-A., No. 1488. 

 //. iticntssata forma tnonilis Barton, 1901, p. 27, PI. IV, fig. 40. 

 Plants up to 20 cm. high, much calcified ; branching in one 

 plane ; segments cuneate or tridentate when bearing branches, 

 all others cylindrical, up to 8 mm. long, 1-2 mm. diam. Periph- 

 eral utricles 30-44 /u diam., adherent for one- third to one-tenth 

 their length, not easily separable : filaments of central strand 

 connected by pits. Fla., W. I. 



The habit is usually quite distinct from that of //. tn'dens, 

 with which it has been generally associated ; in occasional 

 doubtful cases, microscopic examination is needed. 



3. H. GRACILIS Harvey, Ceylon Algae, No. 72 ; Barton, 

 1901, p. 22, PI. Ill, figs. 28-32; Vickers, 1908, p. 24, PI. 

 XXXIV. Fronds of varying length up to 40 cm., much calci- 

 fied below, upper segments less ; branched in one plane ; seg- 

 ments cuneate to subcylindrical, not ribbed, l / 2 -g mm. long, 

 iJ2-ii mm. wide. Filaments of central strand fused in pairs, 

 single fused filaments branching later trichotomously ; periph- 

 eral utricles 30-45 p diam. St. Thomas, Barbados. 



Reported from only two localities within our range, but likely 

 to be found at other points. It has probably been taken for a 

 slender, loosely branched H. Opuntia or H. tridens ; the only 

 sure test would be by microscopic examination. 



4. H. LACRIMOSA Howe, 1909, p. 93, PI. V, fig. i ; PI. VI, 

 figs. 3-11. Plants up to 5 cm. high, strongly calcified ; branch- 

 ing mostly but not exclusively in one plane. Segments obovoid, 

 pyriform or subglobose, occasionally subterete, 1-5 mm. long 

 and broad, solid and stony or the larger ones hollow ; surface 

 smooth and compact. Filaments of central strand fusing in 

 twos or threes at the nodes, sometimes with secondary incom- 

 plete fusions; peripheral utricles obconical, 40-110 /x long, 

 33-37 M diam., in contact for one-tenth to one-thirtieth of their 

 length; subcortical utricles in a single series, 66- no /* diam. 

 W. I. 



