Fig. 1.—Conidia and Hyphæ from Culture in Experimental Ketchup Containing One-sixteenth of One Per Cent of Sodium Benzoate (X 325).
Fig. 2.—Conidia and Hyphæ from Cultures in Experimental Ketchup Containing One-tenth of One Per Cent of Sodium Benzoate (X 325).
CULTURES FROM KETCHUP PRESERVED WITH SODIUM BENZOATE.
DEVELOPMENT.
In developing, the mold forms a white felt-like mass, covering the medium on which it is growing; then as development proceeds, it changes to bluish-green, and finally to a darker, duller color. The change in color is accompanied by a change in structure, the surface becoming powdery in appearance, a slight current of air being sufficient to dislodge a cloud of fine dust. This fine dust is formed of small, spherical bodies, the spores or conidia (from the Greek meaning dust). These need no resting period, but are able to develop at once. When the conidia lodge on a moist substance they swell to a much greater size and then send out a tube from some part of their surface. The tube lengthens and septa form, dividing the tube into sections, or cells. At the same time branches are sent out, which again form other branches. The original conidium sends out a second branch shortly after the first one, and usually from the opposite side, and may even send out a third one. The formation of the septa and the subbranching goes on in all, so that in a short time the branches mat together and form a felt-like cover.