WALL FLOWER.--This flower yields a juice, when expressed with alcohol, from which subsides, on standing, a bright yellow finely divided faecula, leaving a greenish-yellow transparent liquid, only slightly colored supernatant. The faecula spreads well on paper, and is very sensitive to light, but appears at the same time to undergo a sort of chromatic analysis, and to comport itself as if composed of two very distinct coloring principles, very differently affected. The one on which the intensity and sub-orange tint of the color depends, is speedily destroyed, but the paper is not thereby fully whitened. A paler yellow remains as a residual tint, and this on continued exposure to the light, slowly darkens to brown. Exposed to the spectrum, the paper is first reduced nearly to whiteness in the region of the blue and violet rays. More slowly, an insulated solar image is whitened in the less refrangible portion of the red. Continue the exposure, and a brown impression begins to be percieved in the midst of the white streak, which darkens slowly over the region between the lower blue and extreme violet rays. THE RED POPPY yields a very beautiful red color, which is entirely destroyed by light. When perfectly dried on paper the color becomes blue. This blue color is speedily discharged by exposure to the sun's rays, and papers prepared with it afford very interesting photographs.-- Future experiments will undoubtedly more fully develope the photogenic properties of flowers, and practically apply them. Certain precautions are necessary in extracting the coloring matter of flowers. The petals of fresh flowers, carefully selected, are crushed to a pulp in a mortar, either alone or with the addition of a little alcohol, and the juice expressed by squeezing the pulp in a clean linen or cotton cloth. It is then to be spread upon paper with a flat brush, and dried in the air. If alcohol be not added, it must be applied immediately, as the air changes or destroys the color instantly. Most flowers give out their coloring matter to alcohol or water--but the former is found to weaken, and in some cases to discharge altogether these colors; but they are in most cases restored in drying. Paper tinged with vegetable colors must be kept perfectly dry and in darkness.