169. Plants forming felt-like mats on moist soil, attached to sub- 

 merged substrates, or floating entangled masses; coenocytic and 

 tubular, cylindrical and irregularly branched, reproductive organs 

 lateral or on the ends of short branches ^ Vaucheria 



169. Plants forming submerged, felt-Hke mats with horizontal, rhi- 

 zoidal, and erect freely-branched portions (possibly growing 

 on moist soil also); branching dichotomous, with constrictions at 

 the base of the branches and at the place where long, hooked 



sex organ-bearing branches originate. — Dichotoinosiphon 



170. Plants usually corticated ( columnar cells investing the main axial 

 row of cells — PI. 82, Figs. 7, 13); antheridia below the oogonia, 



which have five cells in the coronula Chara 



170. Plants without cortical cells; antheridia lateral at the nodes or 

 apical on short stalks; oogonium with 10 cells in the coronula, 

 arranged in 2 tiers 171 



171. Antheridia terminal on short stalks in the furcations of branch- 

 lets; plants symmetrically branched Nitella 



171. Antheridia lateral at the nodes, beside the oogonia; branching 

 unsymmetrical, some branches long and coarse, giving the plant 



a scraggly appearance Tolypella 



172. Cells flattened dorsiventrally, broadly ovate or ovoid, subspheri- 



cal, or fusiform in outline (Pi. 80, Figs. 1,2) 173 



172. Cells not dorsiventrally flattened; round in cross section (some 

 spp. of Euglena in exception); round, ovoid, pyriform or elongate 



in longitudinal view, sometimes fusiform or subcylindric — .- 174 



173. With 1 flagellum and 1 or more large and conspicuous paramylon 



grains; eye-spot usually clearly evident — Phacus 



173. With 2 flagella, one trailing; food in the form of oil; eye- 

 spot lacking ..__. Gonyostomum 



174. Cells inclosed by a firm brown shell or test (PI. 83, Fig. 1), of 



many shapes and with various decorations.. Trachelomonas 



174. Cells not inclosed by a test .- 175 



175. Cells ovoid or pyriform, rigid, not changing shape in movement; 

 paramylon bodies 2 large lateral rings Lepocinclis 



175. Cells elongate-fusiform, or nearly cylindrical, mostly metabolic 

 (changing shape in movement), or rigid in some species; paramy- 



l6n bodies of various shapes but mostly small and nvunerous Euglena 



176. Chromatophores violet-green, gray-green (plants sometimes 

 appearing blue-green in mass); macroscopic branched thaUi, 



or microscopic cell clusters, or filaments ^ 177 



(see also 183) 



176. Chromatophore or protoplast some other color than gray- 

 green or violet-green 180 



177. Plants attached, macroscopic, multicellular, usually highly 

 branched thalli 178 



177. Plants microscopic, filamentous, growing erect from an attached 

 portion and alternately branched; branches usually simple, and 

 tapering sHghtly toward the apices... Audouinella 



178. Thallus embedded in a soft, copious mucilage, exhibiting a regu- 

 lar plan of branching, with internodes and nodes from which 

 fascicles of branches arise; plants limp and formless when 

 removed from the water Batrachospermum 



[585] 



