of the flower; a morphology of the Cryptogams was as little to be thought of in the condition of microscopy before 1820, as the application of the history of development to the establishment of morphological theories.
De Candolle published his morphology or doctrine of symmetry and his theory of classification together in a book which appeared first in 1813, with the title, 'Théorie Élémentaire de la botanique ou exposition des principes de la classification naturelle et de l'art de décrire et d'étudier les végétaux,' and again in 1819 in an improved and enlarged edition. The second edition will be the one referred to in the further account of his views. The second chapter of the second book concerns us most at present. After alluding to the fact, that anatomy and physiology are concerned with the structure of the individual organ only so far as the power to fulfil its proper function depends on the structure, he points out that the physiological point of view is no longer sufficient when we are engaged in comparing the organs of different plants. Though it is true that the function of the organs is the most important for the life and permanence of the individual, yet we find these functions modified in the case of homologous organs in different plants; for the natural classification we must take into consideration only the entire system of organisation, that is, the symmetry of the organs. All organisms of a kingdom, he continues, have the same functions with slight modifications; the immense amount of variation in systematically different species depends therefore only on the way in which the general symmetry of structure varies. This symmetry of the parts, the discovery of which is the great object in the investigation of nature, is nothing more than the sum total (l'ensemble) of the positional relations of the parts. Whenever these relations (disposition) are regulated according to the same plan, the organisms exhibit a certain general resemblance to one another, independently of the form of the organs in detail; when this general resemblance
