. Carnegie Institution of Washington publication. 48 BACTERIA IN RELATION TO PLANT DISEASES. bottom the water drips to the lower bottom and is quickly converted into steam which streams through a central chimney into the bottom of the sterilizing chamber. The latter has two walls, with a considerable air-space between, open at the bottom. The streaming steam passes over the top of the inner wall downward into this air- space and escapes into the pan as condensation water. Theoretically this is a very perfect sterilizer, and it is so in prac- tice when new, but not infrequently it leaks, and so
. Carnegie Institution of Washington publication. 48 BACTERIA IN RELATION TO PLANT DISEASES. bottom the water drips to the lower bottom and is quickly converted into steam which streams through a central chimney into the bottom of the sterilizing chamber. The latter has two walls, with a considerable air-space between, open at the bottom. The streaming steam passes over the top of the inner wall downward into this air- space and escapes into the pan as condensation water. Theoretically this is a very perfect sterilizer, and it is so in prac- tice when new, but not infrequently it leaks, and sometimes the openings in the upper bottom are too large or become clogged by mud. When in perfect working order it takes only a few minutes to get a temperature of 100° C. Tubes should always be steamed in wire-crates (fig. 44) so that the streaming steam may have full access to all parts. Tubes of media steamed in cans or beakers often spoil. They seem to retain a cushion of air about them which interferes with the action of the steam. Litmus milk.—Litmus milk of a good quality may be made by dissolv-. Fig. ing Merck's dry, lime-free c. p. blue litmus to saturation in distilled water (1:15) and then adding one part of this blue fluid to each fifty parts of milk. The milk should be a deep lavender color. Much inferior litmus is on the market. Large use should be made of this fluid. In addition to observations under "Milk," note how rapidly the litmus reddens, blues, or becomes reduced, and how soon the color returns. Will it return at once on steaming the culture? Rice cooked in milk.—(One or two grams to 10 cc. in each test-tube). This is useful for study of some chromogens. LoeffleSs solidified blood-serum.—Observations under this and the following heads are the same as for gelatin slant cultures. The plant bacteriologist must in general obtain blood-serum from the animal bacteriologist. The solidified serum may also be used plain, i. <-., without the addit
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