. Synopsis of the naviculoid diatoms. Presented to the R. Swedish Academy of Sciences May 10, 1893. Diatoms. '— a- Nav. Hennedyi with cell-contents, 600 times Nav. Lyra var. with cell-contents, 600 times magnified. The most important characteristic of this group consists in the lateral areas, which are to be regarded as lateral expansions of the central nodule. They are more silicious than other parts of the valve, and coherent with the mass of the usually small central nodule. This group, corresponding to the Hennedyees and Lyrees in Van Hburck's Synopsis, com- prises an enormous
. Synopsis of the naviculoid diatoms. Presented to the R. Swedish Academy of Sciences May 10, 1893. Diatoms. '— a- Nav. Hennedyi with cell-contents, 600 times Nav. Lyra var. with cell-contents, 600 times magnified. The most important characteristic of this group consists in the lateral areas, which are to be regarded as lateral expansions of the central nodule. They are more silicious than other parts of the valve, and coherent with the mass of the usually small central nodule. This group, corresponding to the Hennedyees and Lyrees in Van Hburck's Synopsis, com- prises an enormous mass of forms, in which are more transitions than in any other group of navi- culoid diatoms. All the characteristics are subject to so much variation, that I am unable to distinguish more than a very few, well defined species, although besides the numerous pu- blished figures I have examined at least 300 sketches of forms from all parts of the world. I have tried to obtain characteristics from the relative number of the striae and their puncta, but the variation, even in the same species, is too great. The outline of the valve oifers no trustworthy characteristics, the same species occurring with rounded, obtuse and rostrate ends. The breadth and form of the lateral areas are also subject to great variations, so that all possible transitions can be traced from the large lunate areas of N. Hennedyi to the narrow and linear areas of N. Lyra. The presence or absence of markings in the areas offer no characteristics for specific distinction. Inspection of a large number of specimens has induced me to unite in one species a considerable number of forms, hitherto admitted as distinct species. The forms be- longing to N. approximata, N. Hennedyi, N. spectabilis, N. clavata and N. Lyra are numerous, and the simplest and most effective course would perhaps have been to unite these five species, and possibly others; as they all pass by numerous intermediate forms into each Ple
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectdiatoms, bookyear1894
