Mitosis ( Mitotic ) : nuclear division by formation of spireme thread and chrom- 

 osomes. 



Moniliform: resembling a string of beads. 



Monaxial: with one axis or with one row of cells. 



Monoecious: "of one household"; with both male and female sex organs on the 

 same plant. 



Monosiphonous: formed of a single tube or filament, without cross walls. 



Monospores: asexual spores cut off from tips of branches, or from vegetative 

 cells (e.g., some Rhodophyceae ) . 



Monostromatic: referring to a prostrate thallus, one cell in thickness. 



Mother cell: the cell which divides itself (often internally) into daughter cells. 



Motile: able to move; swimming. 



Multicellular: composed of many cells. 



Multiaxial: with more than one axis; with more than one row of cells. 



Multinucleate: with many nuclei. 



Multiseriate: with more than one row of cells; with many filaments. 



Nannandrous: with dwarf male plants, minute male filaments growing epiphyti- 

 cally on the female plant ( Oedogoniaceae ) . 



Nannoplankton: very minute aquatic organisms (see plankton). 



Nannospores: very small vegetative cells arising from rapid cell division. 



Napiform: turnip-shaped. 



Naviculoid: like Navicula; like a little boat. 



Necridium: a dead cell; a somewhat differentiated cell in some filamentous 

 Myxophyceae which permits fragmentation to occur readily. 



Nekton: organisms capable of swimming against water currents. 



Neuromotor apparatus: the bodies and fibrils interconnecting flagella and at- 

 taching them to the centriole and the nucleus (e.g., euglenoids). 



Neutral spore: a vegetative spore arising from increased cell division in certain 

 Rhodophyceae. 



Nodule: a small knob. 



Nonparticulate: referring to substances in solution. 



Obconic: cone-shaped with the broader end foremost. 



Obovoid: inversely ovoid; with the broader end anterior or outermost. 



Obpyriform: inversely pear-shaped, with the broader end anterior or outermost. 



Ochromonad: a type of cell similar to Ochromonas (with two flagella. of un- 

 equal length ) . 



Ocelli: raised thickenings on the walls of diatoms. 



Ocrea: a sheath; a layered envelope. 



Oligotrophic: referring to younger, deep lakes; poor in production. 



Ontogeny ( Ontogenetic ) : life history of an organism. 



Oogamy: reproduction involving gametes of which one is an egg. 



Oogone, Oogonium: one-celled female reproductive organ, usually containing 

 a single egg. 



Oolith: a stone-like concretion involving a fossil surrounded by deposits of 

 calcareous material. 



Oospore: a thick- walled spore formed from a fertilized egg. 



Operculum: a lid or cap. 



Orbicular: spherical. 



Orbiculate: circular in outline. 



Oval: an elongate figure with convex margins and equally rounded at the ends. 



Ovoid: shaped like an egg; an elongate figure with unequal curvature at the 

 poles, one being broader than the other. 



Ovate: see oval. 



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