1146 EXPERIMENT STATION RECORD. 



seasons to test the effect of blue, black, red, and green colored screens on the produc- 

 tion of grain and chaff of wheat. 



In 1904 the wheat grown under the black screen was richest in nitrogen, followed 

 by the specimens grown under green, blue, and red screens. In 1905 the experi- 

 ments were repeated, and in this case the highest amount of nitrogen was found in 

 the plants grown under the green screens, followed by those under the black, blue, 

 and red. 



Incidentally the effect of these different colored screens on germination was tested, 

 and out of 100 grains selected, 92 germinated in the check, 94 under the black, 97 

 under the red, and 99 under the blue and green screens. 



Anatomical and physiological changes produced in tropical plants by 

 change of environment, D. Bois and I. Gallaud (Compt. Rend. Acad. Sci. [Paris'], 

 141 (1905), No. 24, pp. 1033-1035). — Attention is called to the marked physiological 

 and anatomical changes which take place in various economic tropical plants when 

 taken from one region to another, and the failure to secure the successful economic 

 introduction of many plants, such as rubber, fiber plants, etc., is attributed to these 

 changes. 



Wound stimuli, parasitism, and gum flow of the Amygdalaceee, M. W. 

 Beijerinck and A. Rant (Centbl. Bald, [etc.], 2. Alt., 15 (1905), No. 12, pp. 366- 

 375). — On account of the frequent occurrence of gum flow associated with certain 

 diseases of species of Prunus, the authors have investigated the theories of the effect 

 of wound stimuli to gum flow and the relation of parasites to wound stimuli. 



The principal experiments were made with young shoots of the peach and of 

 a reputed hybrid between the peach and almond. The effect of wounding the 

 cambium in both young and old twigs is shown and comparisons are made w r ith the 

 stimulus caused by poisons, heat, etc. The influence of species of fungi in inducing 

 wound stimuli is described, and gum flow is reported as associated w T ith a consider- 

 able number of species. In conclusion comparisons are drawn between this form of 

 gum secretion and the resins and gums produced by other plants. 



Some experiments in the control of color in plants, H. Kraemer (Abs. in 

 Science, n. ser., 23 (1906), No. 585, pp. 423, 4%4). — In a previous publication (E. S. R., 

 16, p. 540) the author shows that the unorganized or cell-sap color substances in 

 plants readily react with various chemicals, producing in many instances marked 

 changes in color. It was found that the majority of plant-color substances turned 

 green when under the influence of calcium hydrate, deep red with organic acids, 

 rich purple with potassium and aluminum sulphate, and blue with iron sulphate. 



In 1904 the author carried on a series of experiments in this Department for the 

 purpose of determining the effects of certain chemicals on the color principles of 

 plants, the material studied being carnations, roses, and pansies, which were grown 

 in the presence of a large number of chemicals. The results published are consid- 

 ered only preliminary, but it was found that in the case of La France roses the petals 

 became of a uniform pink color when the plants were supplied with iron citrate and 

 citric acid. Maroon roses became dark red when the plants were supplied with 

 phosphoric acid, iron and ammonium sulphate, or sulphuric acid. The maroon roses 

 when treated with sulphuric acid were found to take on a crimson color and they 

 also tended to produce single flowers. 



Some factors concerned in color production in a species of Fusarium, J. B. 

 Pollock (Abs. in Science, n. ser., 23 (1906), No. 585, pp. 422, 423). — A series of experi- 

 ments was carried on with species of Fusarium obtained from the cut ends of corn 

 stubble. 



One of the characteristics of the fungus is the bright salmon-pink color which 

 develops on many artificial media under proper conditions. Among the conditions 

 necessary for its development are direct sunlight, in the absence of which only a pale 

 cream color is produced, generally without a tinge of red. Moisture is also an impor- 



