Marine Algae from Eniwetok — DAWSON 
95 
distichous: disposed in two vertical rows; 
two ranked. 
endophytic: growing within another plant, 
epiphytic: growing on another plant, 
heterocysts: cells which are uniformly dis- 
similar in shape and (or) size from their 
neighbors. 
intercalary: inserted between, as opposed to 
terminal or basal. 
medulla: the central or inner tissue of a thallus 
as opposed to the cortex, 
midrib: a vein-like or rib-like thickened axis 
of a blade. 
monosporangium: an asexual reproductive 
organ in the red algae which produces a 
single spore. 
multifarious: disposed in many ranks about 
an axis. 
multiseriate: of more than a single row of 
cells, 
rhizoidal filaments: thick-walled, very long 
cells of exceedingly small diameter running 
vertically between the larger cortical cells 
as in Gelidium. 
rhizoids: small root-hair-like unicellular or 
multicellular outgrowths for attachment, 
saxicolous: growing on rocks, 
stichidium: a club-shaped reproductive branch 
in the red algae producing tetrasporangia. 
tetrasporangium: an asexual reproductive or- 
gan in the red algae which produces spores 
in groups of four. 
trabeculae: bars or strands running from one 
side of a coenocytic thallus to the other, as 
in Caulerpa. 
trichoblast: a branched, colorless, hair-like 
outgrowth produced around the apex of 
certain red algae, usually soon falling away, 
trichome: the individual cellular filament of a 
multicellular blue-green alga, not including 
the sheath. 
tristichous: disposed in three vertical rows; 
three ranked. 
uniseriate: of a single row of cells, 
utricles: the enlarged, bladder-like ends of the 
filaments of Codium which are arranged to 
make up the surface layer of the thallus. 
KEY TO THE GENERA OF MARINE ALGAE 
of Eniwetok 
1. Plants unicellular, or apparently so, mac- 
roscopic or microscopic, spheroidal, 
ellipsoidal or club-shaped 2 
1. Plants multicellular, or, if noncellular 
the thalli macroscopic and not solid 
spheroidal, ellipsoidal or club-shaped . 8 
2. Plants microscopic, less than 40 fi in 
diameter, in pairs or colonies within a 
gelatinous matrix or sheath, sometimes 
(in Entophysalis ) arranged in short fila- 
ments 3 
2. Plants macroscopic, bladder-like 7 
3. Colonies showing no particular orienta- 
tion into basal and apical regions .... 4 
3. Colonies showing orientation of cells 
into basal and apical regions 
Entophysalis (deusta) 
4. Colonies without definite shape; cells 
symmetrically ellipsoidal 5 
4. Colonies with a definite shape; cells 
pear-shaped Gomphosphaeria 
5 . Cells spheroidal, or hemispheroidal when 
divided 6 
5. Cells elongate ellipsoidal 
Coccochloris 
6. Cells usually single or paired, enclosed 
in a thick, gelatinous sheath . Anacystis 
6. Cells forming colonies within a gelatin- 
ous matrix. Entophysalis (conferta) 
7. Thalli spheroidal, attached by small un- 
branched rhizoids cut off by a septum 
from the main cell 
Valonia (ventricosa) 
7. Thalli short club-shaped, attached by 
branched, nonseptate rhizoids 
Boergesenia 
8. Thalli multicellular or noncellular, 
branched if uniseriate 9 
8. Thalli multicellular, but each filament 
consisting of only an unbranched row 
of cells (the false branching in Plecto- 
nema and Scytonema is the result of 
protrusion of a broken trichome through 
a rupture in the sheath) 99 
