Identifier: algvolimyxophy00west Title: Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ Year: 1916 (1910s) Authors: West, G. S. (George Stephen), 1876-1919 Subjects: Algae Publisher: Cambridge [Eng.] The University press Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library

View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book

Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image: evalves, connecting bands, and intercalary bands fit against one another bybevelled and generally curved edges (consult fig. 58 A—C), but the con-nection is in some cases much looser than in others. Some diatoms possess longitudinal septa, which are invariably ingrowthsfrom the intercalary bands. Such septa are always more or less considerably 86 Bacillarieae perforated and approximately parallel to the valve-faces. The number oflongitudinal septa depends upon the number of intercalary bands. InMastogloia each cell has two longitudinal septa, in Tabellaria there arefrom two to twelve or more, and in Tetracyclus and Rhabdonema theremay be as many as twenty. These septa are generally plane, although theymay be undulated, as in Grammatophora. Karsten has distinguished thoseintercalary bands which possess longitudinal septa as intercalary valves(fig. 58 C and D). The perforations are large but variable. Sometimesone large window-like foramen is situated in the median part of the septum,

Text Appearing After Image: Fig. 59. A and B, Tetracyclus lacustris Kalfs ; B is a longitudinal section of cell showing oneof the partial septa. C, longitudinal section of cell of Licmophora Lyngbyei (Kiitz.) Grun,showing partial septum. I) and E, Tabellaria fenestrata (Lyngb.) Kiitz.; Eis a longitudinalsection of cell showing the extent of the septa. F, Climacosphenia moniligera Ehreiib.,section of upper portion of cell to show the perforated septum, s, septum. C and F areafter 0. Miiller. and at other times the septum is only partial, the foramen occupying mostof the median part and the whole of one end (fig. 59-4—E). In Clima-cosphenia each septum has a series of numerous perforations (fig. 59 F).In Denticula the partial longitudinal septa are fused with numerous im-perfect transverse septa which pass inwards from the valves. Thus the interior of the diatom-cell may become chambered in variousways, and as will be noted subsequently these chambers very largelyaccommodate lobes of the chromatophores. SYMMETRY

Note About Images