The relationships between the endosperm and embryo were shown in 1810 by Robert Brown in his monograph on the Australian Proteaceæ. The morphological nature of seed reserves was described by him. He also discovered the functions of the cell nucleus and founded cytology. He showed that the oscillation of minute particles in the fluids of plants when viewed under high microscopic powers, known as the Brownian movement, is due to purely physical causes. Schultze, Unger, and others, working on suggestions previously made by Knight, Robert Brown, and Hooke, discovered the rôle of protoplasm in plant cells. Alexander Braun and De Bary correlated the movements of protoplasm with the locomotory movements of free zoögonidia and the amœboid movements of Mycetozoa. These investigations directed research to further studies of the structure and constitution of protoplasm and helped develop the cellular theory. The Algæ were studied and classified by Naegeli, Unger, Von Mohl, Haustein, and others in 1847-1850. The vascular cryptogams were studied by Hofmeister. He found that the alternation of a sexual with an asexual generation is common to all plants of the mosses, vascular cryptogams, and gymnosperms, as well as among angiosperms. Hofmeister's work led to appreciation of the fact that a natural system of plant classification must be based, not on balancing the values of the morphological parts of fruits and flowers, but on the anatomy of the real and concealed reproductive organs. Fossil botany, or paleophytology, was founded, in 1828, by Adolphe Brongniart. Witham, Goeppert, Unger, Corda, and others helped to advance this science. The publication of Darwin's "Origin of Species" in 1859 found the various botanical sciences already well worked out by numerous capable experts. A huge amount of data and descriptive matter had been assembled and botany, like the other sciences, was ready to be quickened by the Darwinian theories. The idea of a progressive evolution in plants had been suspected by many botanists, but the genius of Darwin developed it. Living plants were pictured as a multitude of units competing for food, light, air, and room for growth, and struggling against unfavorable environments. The classification of tissues was begun, and the phenomena of absorption of water and salts, the ascent of sap, the absorption of minerals and nitrogen, and metabolism and growth were elucidated. Investigations were made into the nature and functions of chlorophyll and other plant substances. These studies resulted in suggesting means for improving crops by artificial selection, as shown in the work of Luther Burbank. CHAPTER XIV GEOLOGY, METALLURGY, AND METEOROLOGY