. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Fig. 78. A, Navicula limosa Kiitz.( x 450). B, Achnantkes flcxella(Kiitz.) Breb. ( x 450). C, NaviculaAmphisbsena Bory ( x 450). D, Kiitz. (x 350). C and Dillustrate the first method of auxo-spore-formation, B the third method,and A the fifth method. A uxospore formation 109 and the significance of this tetrad-division, which precedes conjugation, maylie in the reduction of chromosomes. There yet remains much work to be done on the
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Fig. 78. A, Navicula limosa Kiitz.( x 450). B, Achnantkes flcxella(Kiitz.) Breb. ( x 450). C, NaviculaAmphisbsena Bory ( x 450). D, Kiitz. (x 350). C and Dillustrate the first method of auxo-spore-formation, B the third method,and A the fifth method. A uxospore formation 109 and the significance of this tetrad-division, which precedes conjugation, maylie in the reduction of chromosomes. There yet remains much work to be done on the cytology of auxospore-formation, as most of our present knowledge is based upon a few isolated Rt Fig. 79. Conjugation of Rhopalodia gibba (Kiitz.) 0. Mull. The conjugating cells are seen inthe valve view except in fig. 3, in which they are seen in an oblique girdle view, k, nucleus;kk, small nucleus; gk, large nucleus ; py, pyrenoid; #, gelatinous investment. (FromOltmanns, after Klebahn.) Karsten has stated that the type of auxospore-formation which occursin the greater number of ground species is that in which two auxospores areformed by conjugation (the fifth type described above), but the observationsof those who have spent many years in the investigation of freshwater andlittoral diatoms scarcely support this statement, whereas there is much 110 Bacillariecf evidence to show that the first and fourth types are probably of the mostfrequent occurrence. The most essential feature in the formation of anauxospore is the increase in size of the cell. The first method of auxospore-formation is common in certain species of Melosira, and as the auxosporesgrow into filaments of cel
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