THE GREEN ALGAE OF NORTH AMERICA 393 



The soft stem, usually flattened or canaliculate when dried, 

 and the stout but not very abundant filaments of the head, dis- 

 tinguish this from the other species. 



Var. GRACILIS A. and E. S. Gepp, 1905, p. 2, PI. CCCCLX- 

 VIII, fig. 2 ; P. B.-A., No. 1476. Filaments more abundant, 

 300-400 /txdiam. With the type. 



4. P. PYRIFORMIS A. and E. S. Gepp, 1905, p. i, PI. 

 CCCCLXVIII, fig. i ; P. B.-A., No. 1477. Stipe 1-3 cm. 

 long, 6-7 mm. thick, slightly compressed, hardly entering the 

 head, surface rough ; head pyriform, 5-7 cm. long, 3-4.5 cm. 

 diam., dense, drying glaucous green; filaments calcified, as- 

 cending, densely interwoven, 150-200 /x diam. In shallow water. 

 Fla., Bermuda, Bahama. 



Resembles P. capitatus, but with shorter and relatively stouter 

 stipe, not penetrating far into the head ; the latter is pyriform 

 rather than spherical, and the filaments are more densely matted. 



4. RHIPOCEPHALUS Kiitzing, 1843, p. 311. 



Frond with erect stipe, bearing at the summit a dense cluster 

 of minute, cuneate, flabellate expansions, formed of the laterally 

 united filaments ; otherwise like PeniciUus. 



R. PHOENIX (Ell. and Sol.) Kiitzing, 1849, p. 506 ; P. B.-A., 

 No. 1030; PeniciUus Phoenix Harvey, 1858, p. 46, PI. XLIII.C. 

 .Stipe to 10 cm. high, about 8 mm. diam., terete, slightly taper- 

 ing upwards, strongly calcified, smooth ; the upper part con- 

 cealed by the round, oblong, or conical head ; flabella compos- 

 ing the head 5-20 mm. long, calcified, monostromatic, each 

 composed of the laterally united dichotomous ramification of a 

 single basal filament : filaments 75-100^ diam. Fig. 150. Fla., 

 W. I. 



The flabellately united filaments distinguish this from all 

 species of PeniciUus, and there is no other genus for which there 

 is any danger of mistaking it ; but it varies much in general 

 dimensions, as well as in proportion of parts. In Gepp, 1905, 

 p. 4, the following forms are indicated. 



Forma TYPICUS Gepp, 1905, p. 4. Flabella about 15 mm. 

 long, forming an oblong, smooth head. 



Forma BREVIFOLIUS Gepp, 1905, p. 4. Flabella 5-10 mm. 

 long, generally in densely imbricate, ascending whorls, forming 

 an elongate-conical head ; stipe percurrent through the head. 

 Fla., Bahama, Guadeloupe, Jamaica. 



Forma LONGIFOLIUS Gepp, 1905, p. 4, PI. CCCCLXVIII, 



