Reticulate: netted; arranged in a net- work; covered with thickenings in the 

 form of a net. 



Retuse: rounded at the apex but with an incision (as in heart-shape). 



Rhahdosomes: small rods in the periphery of cells in some dinoflagellates. 



Rhizoidal: root-like, resembling rhizoids. 



Rhizoplast: fibril connecting flagellum base with centrosome; part of the neu- 

 romotor apparatus in flagellated organisms. 



Rhizopodal: moving as an amoeba. 



Rhizopodal tendency: evolutionary trend from a swimming cell to a condition 

 in which the organism is amoeboid. 



Rhomboid: a parallelogram with obUque angles and adjacent sides imequal. 



Rostrate: with a beak. 



Rostrate-capitate: with a beak which has a swoUen tip. 



Rugose: roughened, as with ridges and furrows. 



Saccate: like a sac; balloon-shaped. 



Saccoderm desmids: desmids unconstricted in the mid-region and with the 

 wall in one piece ( cf . placoderm desmids ) . 



Saggitate: arrow-shaped. 



Saprophyte: organism that obtains food from dead organic matter. 



Sarciniform: in the shape and arrangement of a cubical packet. 



Scalariform: ladder-like, referring to conjugation by tubes connecting two 

 filaments. 



Scale-like: like a small husk or membrane. 



Schizophycean phycoerythrin: red pigment in the Myxophyceae. 



Scrobiculate: pitted, usually with round, shallow depressions. 



Scytonemin: a pigment found in the sheath of some Scytovema. 



Semi-anaerobic: see anaerobic. 



Semicell: cell-half of a desmid. 



Semilunar: somewhat crescent-shaped. 



Septa: a cross wall or partition. 



Seriate: in a Unear sequence or series. 



Seta: a hair or bristle; sometimes a tail-piece. 



Setiferous: bearing a seta or hair. 



Sexual auxospore: spore formed by union of gametes, or from parthenogenetic 

 development of gametes ( diatoms ) . 



Sheath: a covering, an envelope, usually relatively thin and composed of 

 mucilage. 



Sigmoid: Hke the letter S. 



Silicious: containing silicon. 



Sinus: the incision of a desmid cell in the midregion; any conspicuous invag- 

 ination. 



Siphon: organ involved in the digestive apparatus of some flagellates. 



Siphonaceous: referring to a tubular thallus which has no cross walls (e.g., 

 Vaucheria ) . 



Spatulate: elongate, gradually enlarged and bluntly rounded at one end. 



Spermatia: cells acting as male gametes; non-motile male cells, as in Rhodo- 

 phyceae. 



Spermatozoid: a male gamete. 



Spermocarp: one of ^he investing cells developed about the fertilized egg 

 ( Coleochaete ) . 



Spongiose: hke a sponge; Uke a soft, thick mat. 



Spicules: needle- like scales or hard bristles. 



Spinescence: spines; spine arrangement. 



[607] 



