58 MARINE ALG 
ORDER UDOTEACE 
Genus Penicillus 
The merman’s shaving-brush, characteristic of coral reefs. 
P. dumentosus. UHoldfast much branched, like a fibrous root, and 
penetrating deep into the coral or sand; stem short, thick, more or less 
flattened, sometimes hollow, covered with velvety scurf; top covered 
with loosely spreading tuft of soft filaments three to six inches long, 
which branch repeatedly in pairs (dichotomous); color deep green. 
When old, these plants are incrusted with a thin, porous layer of car- 
bonate of lime. (Plate VI.) 
P. capitatus. Holdfast a dense mass of fibers two or more inches 
long; stipe one to five inches long, one fourth to one third of an inch in 
diameter, usually cylindrical, sometimes wider at top than at base, 
sometimes flattened ; thickly incrusted with lime, which is smooth and 
often polished; top a dense, spherical mass of filaments one to two 
inches in diameter; filaments branching dichotomously, and rigid from 
incrustation of lime. 
P. Phenix. Stipe cylindrical, one to three inches long, one fourth of 
an inch in diameter, thickly incrusted with lime, smooth; capitulum or 
head ovoid, and composed of filaments which are incrusted with lime 
and coherent, forming many distinct, flat, wedge-shaped, level-topped, 
spreading laming. This species is found at Key West. 
Genus Udotea 
U. flabellata. Short, flattened stem, expanding into a broad, fan- 
shaped, smooth frond, concentrically zoned; margin wavy; thickly 
incrusted with ime. Abundant at Key West. 
U. conglutinata. Deeply descending root; stem expanding into fan- 
shaped frond ; entire, lobed, or irregularly torn; slightly incrusted with 
lime. The frond is composed of longitudinally parallel, adherent fila- 
ments, which are visible, giving a striated, rough surface. (Plate VI.) 
GENUS Halimeda 
This genus resembles the corallines externally, and is abundant 
on coral reefs. It appears as if formed of separate parts, resem- 
bling a series of heart- or kidney-shaped segments strung together. 
The plants are more or less incrusted with lime. The branching 
holdfast grasps particles of sand, and with them forms a solid 
ball. 
Hi. tuna. Articulations roundish or half kidney-shaped, one half to 
three quarters of an inch broad; frond flat, smooth, and thinner than 
most species ; bright green ; somewhat flexible, (Plate VII.) 
