. Annals of applied biology. Biology, Economic; Biochemistry. H, Gr. Thornton 251 As the moisture appears, a slow motility can be observed in the colony, the rods sliding over one another and slowly pushing outward the edge of the colony. Single rods do not appear capable of overcoming the surface tension at the edge of the water film. They have many times been observed pushing outward but do not force their way out from the colony^. Packets of six or more cells, however, are able slowly to press outward the edge of the water film. Consequently, where a packet of cells lies at the edge of the
. Annals of applied biology. Biology, Economic; Biochemistry. H, Gr. Thornton 251 As the moisture appears, a slow motility can be observed in the colony, the rods sliding over one another and slowly pushing outward the edge of the colony. Single rods do not appear capable of overcoming the surface tension at the edge of the water film. They have many times been observed pushing outward but do not force their way out from the colony^. Packets of six or more cells, however, are able slowly to press outward the edge of the water film. Consequently, where a packet of cells lies at the edge of the colony, in such a manner that the rods lie radially, or at right angles to the film edge, they may often be observed. Fig. 1. Bacillus deiidmides. Successive stages in the formation of a process from a 6 hours old surface colony on nutrient agar. to force their way outward producing a small promontory (Fig. 1). But where the outer packets lie so that the cells are oriented tangentially, they do not press away from the centre. The out-pushing of the colony edge is therefore discontinuous so that the colony becomes irregular or lobate. As the water film becomes thicker, the cells move about more actively, and, in the interior of the colony, they often lose their arrange- ment in packets, and where there is most moisture a streaming move- ment of cells may be observed. In each projection of the colony edge, the cells tend to swim outward and to collect at the distal extremity, 1 An attempt was made to modify this condition by adding 0-05 per cent, saponin to the medium in order to lower the surface tension of the film. The saponin, however, caused abnormal growth of the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Association of Applied Biologists; Association of Economic Biologists. [Wellesbourne
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