. Fungous diseases of plants : with chapters on physiology, culture methods and technique . Fungi in agriculture. GERMINATION STUDIES 59. possible. It is sometimes desirable to distribute the spores pre- viously in a drop or small quantity of water, otherwise one may get too many in the culture drop. The covers are then inverted over the glass ring and pressed down so as to leave only one minute unsealed area. It is an unwise and an inaccurate plan to use in the bottom of the cell any other liquid than that used in the culture drop. This must be so in order that there may be no differ- ences o
. Fungous diseases of plants : with chapters on physiology, culture methods and technique . Fungi in agriculture. GERMINATION STUDIES 59. possible. It is sometimes desirable to distribute the spores pre- viously in a drop or small quantity of water, otherwise one may get too many in the culture drop. The covers are then inverted over the glass ring and pressed down so as to leave only one minute unsealed area. It is an unwise and an inaccurate plan to use in the bottom of the cell any other liquid than that used in the culture drop. This must be so in order that there may be no differ- ences of vapor pressure, and consequently no evap- oration from drop to'liquid below, or vice versa. For instance, it would be man- ifestly absurd to test ger- mination in a drop of, say, Fig. 13. Rings for Drop Cultures S per cent alcohol above if "< cemented to slide ; i, in Petri dish with filter paper there were only pure water below. If there is danger of contami- nation below, and consequent interception of the light, thorough sterilization must be given beforehand. If the drop cultures are made as soon as the slides are prepared, sterilization should not be necessary, since all parts are flamed. Sterilization may be given at any time, however, previous to the ringing with vase- line. It is usually sufficient to sterilize the cells in a dry oven at a temperature of from 1100 to 1150 C. This temperature melts the wax, but if the slides are level, there is no danger that the cells will slip. A temperature much higher is not to be recom- mended. Another convenient method of sterilization is by means of formalin. The cells are filled with a solution of from 3 to 5 per cent formalin, and this is allowed to stand for half an hour; then on being rinsed with distilled water, again filled with the water, and left for ten minutes they will be found sterile. The cells should then be inverted and dried before the ringing with vaseline is effected. By this process some cells will bec
Size: 2111px × 1184px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorduggarbe, bookcentury1900, bookdecade1900, bookyear1909
