RESUME.
Beginning with the most minute and simplest of plants, such as are found in every pond and ditch, and comparing them with the different sea-weed, Fungi, etc., we found, notwithstanding minor differences, that their structure was essentially the same, cellular; offering no trace in their organization of stem and leaves. Passing from the cellular plants, through transitional forms, to the Liverworts, we noticed that the lower forms of this are still cellular, while the higher exhibit the beginning of a separation into stem and leaves. Forms like these lead the way to the Mosses, in which the stem and leaves are well defined. The Ferns, while agreeing with the Mosses in having stem and leaves, offer an advance in their organization, since their stem contains vessels with more or less woody tissue. Passing from the Ferns to the closely allied Club-mosses, we found in them the links binding the Flowerless with the Flowering plants. Taking up next the Cycadae and Coniferae, we saw how naturally they preceded the Endogens and Exogens. Finally, in the different kinds of Exogens we saw an ascending series, as illustrated in the flower of the Spurge, Goose-foot, Violet, Morning-glory. Our brief survey of plants may be expressed in the following conclusion: The vegetal kingdom may be represented by a tree, of which the stems and branches are the classes, orders, etc. The trunk of this tree, being composed of the simplest forms, grows gradually upwards into more complex ones, finally developing the noblest of trees, the most beautiful of flowers. We hope to show in our next chapter that the petrified remains of the animal and vegetal kingdoms offer such a progress from lower to higher forms.
