Bulletin Volume 166-190 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 Excerpt: ...effects resulting from growing diseased plants in suffused light, but Lodewijks was the first to really study the effects produced by colored light, although Bauer appears to have made some observations on this point. As in no case could the writer find that Lodewijks in his work had reinoculated from the apparently cured plants to healthy ones, to prove the presence or absence of the causal agent, and as it is often present and active in apparently healthy leaves of diseased plants, as has been shown many times, it was thought necessary to settle the point as to the presence or absence of the causal agent in plants treated as in Lodewijks' work. Method.--The method of treatment of diseased plants was in every way similar to that employed by Lodewijks as to texture of cloth, methods of covering the plants, etc. The cloth covers were held away from the plant by means of wire hoops, and the cloth was tied around the stem of the plant below the diseased leaves. Plate V. shows a hood in place over a field-grown plant, and gives a clear idea of the arrangement of the hoops, etc. The cloth used was a coarse grade of cotton, and the colors were cadmium orange, ox-blood red and indulin blue.1 Plants showing well-developed symptoms of the mosaic disease were selected for the experiment, none of which had less than four characteristically diseased leaves, the lower remaining leaves apparently healthy. The hoods were placed over the diseased leaves as above noted, and left on for the required time, in most of the experiments twenty to thirty days. At the end of this period the hoods were removed and the plants carefully examined for visible symptoms of the disease. Two leaves from the upper (i.e., the part under the hood) portion of the plant were removed under absolu...