. Carnegie Institution of Washington publication. THE DISEASE. (iicooRAPHICAL DISTRIBUTION. Geographical distribution is an exceedingly interesting problem to many naturalists. The writer shares this feeling and has made ever}' effort to determine it, as far as possible, for each disease. There are, however, still many gaps in our knowledge—the whole subject is so new, and information from all parts of the world is desired. The inner temperature of plants conforms nearly or quite to that of the surrounding medium, and we might therefore expect, in some cases at least, to find a rather more sha

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. Carnegie Institution of Washington publication. THE DISEASE. (iicooRAPHICAL DISTRIBUTION. Geographical distribution is an exceedingly interesting problem to many naturalists. The writer shares this feeling and has made ever}' effort to determine it, as far as possible, for each disease. There are, however, still many gaps in our knowledge—the whole subject is so new, and information from all parts of the world is desired. The inner temperature of plants conforms nearly or quite to that of the surrounding medium, and we might therefore expect, in some cases at least, to find a rather more sha
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Image ID: RFRGGX
. Carnegie Institution of Washington publication. THE DISEASE. (iicooRAPHICAL DISTRIBUTION. Geographical distribution is an exceedingly interesting problem to many naturalists. The writer shares this feeling and has made ever}' effort to determine it, as far as possible, for each disease. There are, however, still many gaps in our knowledge—the whole subject is so new, and information from all parts of the world is desired. The inner temperature of plants conforms nearly or quite to that of the surrounding medium, and we might therefore expect, in some cases at least, to find a rather more sharply restricted distribution than in diseases of the warm-blooded animals. From theoretical con- siderations we should expect the distribution of plant diseases to be more like that of diseases of fish and other cold-blooded animals. Whenever the bacterium is able to endure as wide a range of temper- ature as the host-plant, we should expect to find it as widely distrib- uted. SIGNS OF THE DISEASE. Great care should be exercised in the description of the physical signs and of the lesions due to the parasite, so that the disease may be identified from these alone, if necessary. A great many cases should be examined and the signs must be recorded in detail and with great accuracy. It should be remembered that here is a frequent opportunity for error to creep in, lg' ' since the plant may be affected by two distinct diseases which have been confused. Good figures are always desirable, but are not absolutely essential. If possible, however, photographs, pen or pencil drawings, and good water-color sketches should be secured. *Fic. 4.—Cross-section of a turnip root, showing vessels occupied by Bacterium cainpestre as the result of a pure-culture inoculation hy means of needle-pricks on the leaves. Material fixed in strong alcohol, infiltrated with paraffin, cut on the 'microtome, stained with safranin-picro-nigrosin, and the differential washing stopped at just the right stage.

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