For the Vegetable Kingdom it is impossible to give any list composed with the same degree of elaboration as has been attained in the classification of animals. Modern plants are, it is true, as well known and as correctly grouped as modern animal life-forms; but our knowledge of fossil botany is not at all equal to our knowledge of fossil animals. The most minute divisions as well as the most important of botanical classifications are dependent upon the more fully developed and most perishable parts of vegetable organisms—the flowers and the fruits or seeds. Of these the former, the most essential of all, have rarely indeed, if ever, been preserved. One or two doubtful instances have been stated; but these have been by others disputed as being only incipient buds or leaflets, or as accidental appearances, and the investigator of the extinct forms of the vegetable creations of past geological ages has, at the best, to infer from the remains of leaves, branches, or stems, usually more or less decayed, the probable class to which the originals—often, indeed generally, of very different structures and organic characters from his existing types—belong. Not uncommonly, indeed, his only guides are vague and indefinite resemblances of form. Still, however, if it be essential for the attainment of a knowledge of the exact concatenation of past events in the succession of organic life on our planet, it is equally as important to note whether plants have been progressive in their development, as to determine this point in relation to the animal-kingdom.