THE GREEN ALGAE OF NORTH AMERICA 399 



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

 tripartita 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. tridens, those 

 with many cylindrical segments as H. incrassata. Both forms 

 are found together in Florida and the West Indies. 



2. H. MONILE L,amouroux, 1812, p. 186 ; P. B.-A., No. 1488. 

 H. incrassata forma inonilis 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 i^ 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 //. tridens, 

 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, ^2-9 mm. long, 

 1^2-11 mm. \vide. Filaments of central strand fused in pairs, 

 single fused filaments branching later trichotomously ; periph- 

 eral utricles 30-45 ^ 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 b) r 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 /u, long, 

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

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

 W. I. 



