. Fresh-water biology. Freshwater biology. THE FRESH-WATER ALGAE 141 S3 (52) Colony a compact cushion;. stalks encrusted with lime. Oocardium Nageli. Cells broad, middle constriction slight, chromatophores two, pyrenoid in each. Stallis closely placed so that the enveloping cylindrical lime sheaths make a honeycomb-like structure. They are sometimes branched and imbedded in the free end of each is a single cell, placed transversely. It occurs where water trickles over limestone rocks, and is also reported as being found in mountain streams. Fig. 133. Oocardium stratum Nageli. X 485. Portion o£
. Fresh-water biology. Freshwater biology. THE FRESH-WATER ALGAE 141 S3 (52) Colony a compact cushion;. stalks encrusted with lime. Oocardium Nageli. Cells broad, middle constriction slight, chromatophores two, pyrenoid in each. Stallis closely placed so that the enveloping cylindrical lime sheaths make a honeycomb-like structure. They are sometimes branched and imbedded in the free end of each is a single cell, placed transversely. It occurs where water trickles over limestone rocks, and is also reported as being found in mountain streams. Fig. 133. Oocardium stratum Nageli. X 485. Portion o£ figure. (After Seim.) 54 (49) Cells with spines 55 55 (56) Two or four spines on each cell-half . . Arthrodesmus Ehrenberg. General characteristics as in Cosmarium, except that each cell-half is fur- nished with two or four long spines, and the end view shows no lateral rounded prominences. The spines in Arthrodesmus are all arranged in one plane, while in Xantkid- ium they may be arranged in two planes. Fig. 134. Arthrodesmus convergens Ehrenberg. X about 250. (Original.) 56 {ss) Two rows of strong spines on each cell-half 57 57 (58) Spines simple Xanihidium Ehrenberg. Cells oval or nearly round, with deep, narrow, central constriction; end view elhptical, often with protruding sides; membrane with two rows of strong, horn-hke spines; chromatophore parietal, more or less divided, with several pyrenoids. As in Arthrodesmus the presence and the-nature of the spines distin- guish the genus from certain species of Cosmarium. Fig. 135. Xanthidium fasciculatum "Ehienhag, X about 300. (Original.) 58 (57) Spines branched Schizocanthum Lundell. Characteristics similar to those of Xanthidium, except that the spines are thick, short, and branched at the ends. West believes that Schizocanthum should be included under Xanthidium as the only difference is in the spines, and there is too much variation in these, he thinks, to make separate genera. Fig. 136. Schizocanthum armatum Lunde
Size: 1787px × 1399px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
