HOW TO KNOW THE FRESH-WATER ALGAE 



OBLATE-SPHEROID, a figure 



which is a flattened 



sphere; an almost globular 



figure flattened on one 



side. (See Fig. 355) 

 Ochrorr.onas, Synonym for 



Chlorochromonas, 135 

 Oncobyrsa 1 77 



rivularis 1 77 

 Onychonema 88 



filiforme 88 



laeve var. latum 88 

 Oocardium 99 



stratum 99 

 Oocystaceae 1 29 

 Oocystis 62, 85; also 6, 36, 



37 



Borgei 62 



Eremosphaeria 62 

 OOGONIUM, a female sex 



organ, usually an enlarged 



cell; an egg case. 

 OOSPORE, a thick-walled 



resting spore formed from 



a fertilized egg. 

 OPAQUE, not permitting the 



transmission of light. 

 Ophiocytium 134, 138, 140, 



142; also 139 



cochleare 1 34 



desertum var. minor 1 34 



gracilipes 1 34 



parvulum 1 34 

 Ophrydium 65 

 Order, defined 3 

 Oscillatoria 161; also 157, 



158, 159, 163 



rubescens 1 6 1 



splendida 1 6 1 

 Oscillatoriaceae 158 

 Ourococcus 64, 69 



bicaudatus 64 

 OVAL, an elongate, curved 



figure with convex margins 



and with ends broadly and 



symmetrically curved but 



more sharply so than the 



lateral margins. Fig. 358 



Figure 358 



OVOID, shaped like an egg; 

 a curved figure broader at 

 one end than at the other 

 Fig. 359 



Pachycladon 85 

 umbrinus 85 



Palmella 38, 41 ; also 40 

 miniata 38 

 mucosa 38 



Palmellaceae 99 



Palmella Stage of Chlamy- 

 domonas 40 



Palmellococcus 82, 85 

 miniatus 82 



Palmodictyon 43, 100, 110 

 varium 43 

 viride 43 



Pandorina 28; also 26 

 morum 28 



PARAMYLUM, a solid, 

 starch-like storage product 

 in the Euglenophyta. 



Paranema 23 



PARASITIC, living on or in 

 another organism at the 

 expense of the host; often 

 pathogenic. 



PARIETAL, along the wall; 

 arranged at the circum- 

 ference; marginal as op- 

 posed to central or axial 

 in location. Fig. 360 



Figure 359 



Figure 360 



Pascheriella 27; also 29 

 tetras 27 



PEAR-SHAPED, a figure 

 which is elongate and 

 ovate, wider at one end 

 than at the other, usually 

 distinctly narrowed in the 

 midregion. 



PECTIN; a gelatinous carbo- 

 hydrate deposited in the 

 cell or in the cell wall of 

 many algae. 



Pectodictyon 43 

 cubicum 43 



PECTOSE, See Pectin 



Pediastrum 55, 56; also 36 

 biradiatum var. emargina- 

 tum 55 

 Boryanum 55 

 obtusum 55 

 simplex 55 

 tetras 55 



PEDICEL: a small, basal 

 stalk. 



PELLICLE, the outer mem- 

 branous covering as in the 

 Euglenophyta; a skin. 



Penium 72 



margaritaceum 72 



PENNALES, a subclass of the 

 Diatomaceae in which the 

 cells are bilaterally sym- 



metrical and in which wall 

 decorations are bilateral 

 in arrangement from a 

 longitudinal axis, 186. 



PERFORATE, with openings; 

 with pores. 



PERIDININ, a brown pigment 

 characteristic of the Dino- 

 flagellatae. 



Peridinium 152; also 153 

 wisconsinense 1 52 



PERIPHERY, the outer boun- 

 dary; the surrounding out- 

 er part. 



PERIPLAST, see Pellicle. 



Perone 1 33 

 dimorpha 1 33 



Peromelia 135, 142 

 Hyalothecae 135 



Phacotus 32; also 33 

 lenticularis 32 



Phacus 24; also 25 

 curvicauda 24 

 triqueter 24 



Phaeophyta 2, 9, 11 



Phaeosphaera 1 56 

 perforata 1 56 



Phaeothamnion 1 44 

 confervicola 1 44 



Phormidium 163, 164 

 amoiguum 163 

 favosum 163 

 inundatum 1 63 



PHOTOSYNTHESIS, physiolo- 

 gical process by which 

 plants with chlorophyll 

 manufacture c a r b o h y- 

 drates in the presence of 

 light. 



PHYCOCYANIN, a blue pig- 

 ment found in the Cyano- 

 phyta and the Rhodophy- 

 ta. 



PHYCOERYTHRIN, a red pig- 

 ment found in the Rho- 

 dophyta and in some Cy- 

 anophyta. 



PHYCOPYRRIN, a red or red- 

 dish-brown, water - soluble 

 pigment in the chromato- 

 phores of the Dinoflagel- 

 latae. 



Phyllosiphon, 66, 123; also 

 13 

 Arisarii 66 



Phylum, defined, 2 



Phymatodocis 91 

 Nordstedtiana 91 



PIGMENTATION; PIGMENTS, 

 colored substances, either 

 localized in special bodies 

 (plastids) within the cell, 

 or in solution within the 

 cytoplasm. 



PIGMENT - SPOT, see Eye- 

 spot 



Pithophora 118, 121 

 Mooreana 1 1 8 

 Oedogonia 1 1 8 



PLACODERM DESMIDS, re- 

 ferring to those desmids 

 which have the cell wall 

 composed of two sections 

 that are adjoined in the 

 midregion of the cell 

 where there often is a 

 constriction so that "semi- 

 cells" are formed. 



206 



