of Celsius Linnæus conceived the ground-plan of the system of classification by which he was to revolutionize botanical science. The system, since modified by the advance of knowledge, was based on external resemblances. The great work of Linnæus was constructive, not interpretative; and he lived in a period that may be called the renaissance of science.
Linnæus' work was a great step forward, and his system of classification was based on the reproductive organs (stamens and pistils) of plants. The number of species known to Linnæus in 1753, when he published his Species Plantarum, amounted only to 7300. The Linnæan division of plants is into twenty-four classes, depending on the number, position, relative proportion, and combination of the stamens; and the first eleven classes are distinguished solely by the number of the stamens, such as the monandria (one stamen), diandria (two stamens), triandra (three stamens), etc. The twelfth and thirteenth classes are characterized by the situation as well as number of the stamens; the fourteenth and fifteenth classes by the number and relative proportion of the stamens; from the sixteenth to the nineteenth classes, flowers are distinguished by the combination of the stamens with each other; the twenty-first, twenty-second, and twenty-third classes are characterized by the stamens and pistils being in separate flowers; and, finally, the twenty-fourth class, which comprises the Cryptogamia or flowerless plants—