Note on the Cytology of Calothrix fusca

NOTE ON THE CYTOLOGY OP OALOTHEIX FUSCA. 623 Note on the Cytology of Calothrix fusca. Dr. IV. II. Swelleiigrcbel, Amsterdam. With Plate 32. WHILE studying the cytology of several Trichobacterinse I came across a representative of the group of OyanophycesB, the study of which may cast perhaps some light on the question of relationship between Cyanophyceae and Bacteria. I found Calothrix fusca in aquaria among large quanti- ties of Glceocapsa ; I never found it not associated with those algas.

It seems not impossible that a symbiotic relationship exists between those two algEe, a relationship which would be obviously beneficial to Calothrix, this species being more or less deprived of chlorophyll. This question, however, must remain for the while a mere hypothesis, because I was not able to study the question more thoroughly. The dimensions of the cells are very variable. At the end of the cell-filaments the cells are rather short (from 3'6JU— 7-2 ju), but lengthen towards the base (from 7 - 8 /j—10'8/x) ; their breadth is from 3 - 6ju—7'2fj. The filaments which are enclosed in thick hyaline sheaths are pseudo-ramified. Each pseudo-ramification possesses at its base a heterocyst and some concave cells. To study the cytological details the cell-filaments were fixed in Pfeiffer's solution, washed jn alcohol 60 per cent., after the ordinary passages through alcohol embedded in 624 N. H. SWBLLENGREBEL. pai'affin (52°), and cut in sections from 4—6ju thick. The sections were washed in xylol and stained with iron-hema- toxylin (Heidenhain). I shall not enumerate here the different papers which have been published about the cytology of CyanophyceEe. For reference to them the very complete works of Kohl, 1 Fischer, 2 and Guillierrnond...

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