164 



FRESH-WATER BIOLOGY 



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. 



^_ __ _ ^ . ,, _, .- I .. — 7rr-,r--_ Fig. 219. Planktonema lauter- 



(r^^nZsB^±L- i h^'^Q^^ "■ Q O^ ^Tr^r:?-- — ,^_ _^_ homii Schmidle. X about 1000. 



^^"^--^g^ g.^^.-W'-^lIII (After Schmidle.) 



212 (199, 211, 213) Chromatophore a parietal network. Microspora Lagerheim. 



Chromatophores band-like or netted and thickened at intervals; 

 membrane often becoming fraii;mcntcd into ll-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. 



Chromatophores many, parietal, disc-shaped. Filaments 

 fine, unbranched, rarely {Aeronemmn) branched. Repro- 

 duction by mono-ciliate zoospores 214 



Filaments unbranched, at first attached: no pyrenoids. 



Trihonema Derbes and Solier. 



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

 breadth,' sometimes shghtly 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 ciUum, and no pigment spot. 

 Resting cells may occur. 



Structure of cells and zoospores as in Trihonema; 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 Trihonema, but liberated through a dis- 

 solved p>ortion of the membrane, instead of through a circular split dividing the membrane into 

 two portions. Resting cells may be formed. 



Fig. 220. Microspora 

 amaena Lagerheim. 

 X 345- (After West.) 



213 (199, 211, 212) 



214 (215, 216) 



Fig. 



221. Tribonema minor Klebs. 

 (Original.) 



X800. 

 215 (214, 216) 



Fig. 232. Bumilleria 

 sicula Borzi. X about 

 330. (After Borzi.) 



216 (214, 215) 



Structure of cells and zoospores as in Trihonema. Filaments 

 minute, richly branched, easily passing into a unicellular 

 condition Aeronemmn Snow. 



Chromatophores pale, sev- 

 eral in a cell, without pyrenoids 

 and olosely 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 

 Gemeck, though the branching 

 is much more abundant than 

 is described in that form. 



Fig. 223. Aeronemum polymor- 

 phum Snow. X 225. (Original.) 



