The efforts of these two scientists were directed towards obtaining a system which should aim at clearness, simplicity, and precision, and at the same time be governed by the natural affinities of plants.

The natural system, as finally propounded by them, is based on the number of cotyledons, the structure of the seed, and the insertion of the stamens.

Succeeding writers on botany have made various modifications of this system, but nevertheless it stands as the foundation-stone of modern botanical classification.
APPENDIX REFERENCE LIST CHAPTER I SCIENCE IN THE DARK AGE (1) (p.

4).

James Harvey Robinson, An Introduction to the History of Western Europe, New York, 1898, p.