164 



FRESH-WATER BIOLOGY 



FIG. 220. Micros Pora 

 amaena Lagerheim. 

 X 345. (After West.) 





FIG. 



221. Tribonema minor Klebs. 

 X 800. (Original.) 



215 (214, 216) 



Planktonema resembles in many respects the form described by Wittrock as Binuclearia but 

 Schmidle makes it a new genus. The two genera should be made the subject for further in- 

 vestigation. 



^-^A -,*~*, ,"r^i if V^-Vi /fv.->^^, FIG. 219. Planktonema lauter- 



(jp QG&rft) (}*-* -'W 1 (J '-.d|mvr-'-^_ . -MJ... ,., bornii Schmidle. X about 1000. 



^-O^ Q^SUKgSffCC (After Schmidle.) 



212(1 99, 211, 213) Chromatophore a parietal network. Microspora Lagerheim. 



Chromatophores band- like or netted and thickened at intervals; 

 membrane often becoming fragmented into H-shaped pieces. Repro- 

 duction by macrozoospores and microzoospores. 



Filaments free, unbranched; sometimes resembling Conferva. Mem- 

 brane thick, somewhat gelatinous, and distinctly made up of H-shaped 

 pieces, the ends of the H either just meeting or overlapping. Reproduc- 

 tion by macrozoospores with four cilia, and microzoospores with two cilia. 



213 (199, 211, 212) Chromatophores many, parietal, disc-shaped. Filaments 



fine, unbranched, rarely (Aeronemum) branched. Repro- 

 duction by mono-ciliate zoospores 214 



214 (215, 216) Filaments unbranched, at first attached: no pyrenoids. 



Tribonema Derbes and Solier. 



Filaments light green, soft to the touch. Length of cells one to several times the 

 breadth, sometimes slightly swollen at the middle. Chromatophores from two to many, small, 



parietal. Reproduction by zoospores, one or two of 

 which are formed in a cell and liberated by the 

 membrane falling into H-shaped pieces. Zoospores 

 obovate, asymmetrical, with two Chromatophores in 

 the anterior part, one cilium, and no pigment spot. 

 Resting cells may occur. 



Structure of cells and zoospores as in Tribonema; filaments 

 composed of segments of 4 to 8 cells; each formed from the 

 contents of a single vegetative cell, the ruptured wall of 

 which is visible at the end of the segment. Division rarely 



longitudinal Bumilleria Borzi. 



Filaments usually short. Zoospores the same as in Tribonema, but liberated through a dis- 

 solved portion of the membrane, instead of through a circular split dividing the membrane into 

 two portions. Resting cells may be formed. 



FlG. 222. Bumilleria 

 sicula Borzi. X about 

 330. (After Borzi.) 



2 1 6 (214, 215) Structure of cells and zoospores as in Tribonema. Filaments 

 minute, richly branched, easily passing into a unicellular 

 condition . Aeronemum Snow. 



Chromatophores pale, sev- 

 eral in a cell, without pyrenoids 

 and oiosely applied to the mem- 

 brane. Reproduction by zoo- 

 spores which have a single cili- 

 um, a small chromatophore, and 

 a pigment spot. They move 

 with an amoeboid motion. This 

 may be the same as Monocilia 

 Gerneck, though the branching 

 is much more abundant than 

 is described in that form. 



FlG. 223. Aeronemum Polymor- 

 phum Snow. X 225. (Original.) 





