HOW TO KNOW THE FRESH-WATER ALGAE 



PLANE (END WALLS), 

 smooth, not folded walls; 

 opposite of replicate. Fig. 

 361 



D^^U 



Figure 361 



PLANKTON: organisms drift- 

 ing in the water, or if 

 swimming, not able to 

 move against currents. 



Plankton Net 14 



Planktosphaeria 48, 62 

 gelatinosa 48 



PLASTID, a body or organ- 

 elle of the celle, either 

 containing pigments or in 

 some cases colorless. 



PLATE, sections, polygonal 

 in shape, composing the 

 rell wall of some Dino- 

 flagellate (the thecate or 

 armored dinoflagellates). 

 Fig. 362 



POLYGONAL, many sided. 



POLYHEDRAL, a figure with 

 more than four sides. 



Porphyridium 1 30 

 cruentum 1 30 



Porphyrosiphon 1 62 

 Notarisii 1 62 



POSTERIOR, toward the rear; 

 the end opposite the for- 

 ward or anterior end of a 

 cell or of an organism. 



Prasinocladus 1 00 

 lubricus 100 



Prasiola, 98; also 92 

 crispa 98 



Preserving; Preserving Fluids 

 16 17 



PROCESS, an extension of a 

 cell, or of a cell wall, or 

 of a thallus; a horn, arm, 

 or abrupt protrusion from 

 a plane surface. Fig. 363 



Figure 362 



Platydorina 26 



caudatum 26 

 Platymonas 31 



elliptica 3 1 

 Plectonema 161 



Wo//ei 161 

 Pleodorina 30, also 29 



californica 30 



illinoisensis 30 

 Pleurocapsa 1 77 



minor 177 

 Pleurococcus 53, 62, 83 



vulgaris 53 

 Pleurodiscus 94 



purpureus 94 

 Pleurogaster 139, 140 



lunaris 1 39 

 Pleurotaenium 71; also 72 



nodosum 7 1 



trabecula 7 1 

 POLAR; POLE, referring to 



the two opposite ends of 



a cell or an organism, 



or to differentiate points 



in a circular cell; the ends 



of an axis. 

 Polvblepharides 35 



fragariiformis 35 

 Polyedriopsis 86, 87 



quadrispina 86 



spinulosa 86 



PSEUDOPODIUM, meaning a 

 false foot; locomotory or- 

 gan formed by lobe-like 

 extension of the proto- 

 plasm, found in some 

 Chrysophyta and in the 

 Sarcodina Protozoa. 



Pseudotetraedron 1 37 

 neglectum 1 37 



Pseudoulvella 1 1 5 

 americana 1 1 5 



PSEUDOVACUOLE, meaning 

 a false vacuole; a pocket 

 in the cytoplasm of many 

 blue-green algae which 

 contains gas or mucilage, 

 is light-refractive. (See 

 Microcystis, Fig. 318.) 



Pteromonas .33 

 aculeata 33 



PUNCTAE, minute, pin-point 

 pores within the cell wall; 

 minute pits either extend- 

 ing completely through 

 the wall or not. Fig. 365 



' "«• • • * • • J*« L w^ 



Figure 363 



Protococcus 53, 62, 83; also 

 104 

 viridis 53 



Protoderma 1 1 4 

 viride 1 1 4 



PROTONEMA, the filament- 

 ous stage in the develop- 

 ment of moss plants. 



PROTOPLAST, the living part 

 of a cell; the cell mem- 

 brane and its contents, 

 usually inclosed by a cell 

 wall of dead material. 



Protozoa 2, 12, 23 



PSAMMON, the organisms 

 inhabiting the soil (espe- 

 cially sand) above the 

 high water level of lake 

 or river beaches. 



Pseudochaete 1 1 2 

 gracilis 1 1 2 



PSEUDOCILIA, meaning false 

 cilia; flagella-like struc- 

 tures not used for locomo- 

 tion. 



PSEUDOP ARENCHYMA- 

 TOUS, a false cushion; a 

 pillow-like mound of cells 

 (usually attached) which 

 actually is a compact of 

 short, often branched fila- 

 ments. Fig. 364 



Figure 365 



PYRAMIDAL; PYRAMIDATE, 

 in the shape of a pyra- 

 mid; a pointed, 3-sided 

 figure with a broad base. 

 Fig. 366 



Figure 366 



10 



Pyramimonas 35; also 

 tetrarhynchus 35 



PYRENOID, a protein body 

 around which starch or 

 paramylum collects in a 

 cell, usually buried in a 

 chloroplast but sometimes 

 free within the cytoplasm. 



PYRIFORM, see Pear-shaped 

 Fig. 367 



Figure 364 



Figure 367 

 Pyrrhophyta 8, 11, 82 



207 



