A second doubt as to the existence of this primitive flora may be based on the statement that it included the highest forms of plants. Had it consisted only of low and imperfect vegetables, there might have been much less difficulty in admitting its probability. Farther, we find that even in the Carboniferous period scarcely any plants of the higher orders flourished, and there was a preponderance of the lower forms of the vegetable kingdom. We have, however, in geological chronology, many illustrations of the fact that the progress of improvement has not been continuous or uninterrupted, and that the preservation of the flora and fauna of many geological periods has been very imperfect. Hence the occurrence in one particular stratum or group of strata of few or low representatives of animal and vegetable life affords no proof that a better state of things may not have existed previously. We also find, in the case of animals, that each tribe attained to its highest development at the time when, in the progress of creation, it occupied the summit of the scale of life. Analogy would thus lead us to believe that when plants alone existed, they may have assumed nobler forms than any now existing, or that tribes now represented by few and humble species may at that time have been so great in numbers and development as to fill all the offices of our present complicated flora, as well as, perhaps, some of those now occupied by animals. We have this principle exemplified in the Carboniferous flora, by the magnitude of its arborescent club-mosses, and the vast variety of its gymnosperms. For this reason we may anticipate that if any remains of this early plant-creation should be disinterred, they will prove to be among the most wonderful and interesting geological relics ever discovered, and will enlarge our views of the compass and capabilities of the vegetable kingdom, and especially of its lower forms.