The stemmed plants, or Cormophytes, in the organization of which the difference of axial-organs (stem and root) and leaf-organs is already developed, form at present, and have, indeed, for a very long period formed, the principal portion of the vegetable world. However, this was not always the case. In fact, stemmed plants, not only of the flowering group, but even of the prothallus group, did not exist at all during that immeasurably long space of time which forms the beginning of the first great division of the organic history of the earth, under the name of the archilithic, or primordial period. The reader will recollect that during this period the Laurentian, Cambrian, and Silurian systems of strata were deposited, the thickness of which, taken as a whole, amounts to about 70,000 feet. Now, as the thickness of all the more recent superincumbent strata, from the Devonian to the deposits of the present time, taken together, amounts to only about 60,000 feet, we were enabled from this fact alone to draw the conclusion—which is probable also for other reasons—that the archilithic, or primordial, period was of longer duration than the whole succeeding period down to the present time. During the whole of this immeasurable space of time, which probably comprises many millions of centuries, vegetable life on our earth seems to have been represented exclusively by the sub-kingdom of Thallus plants, and, moreover, only by the class of marine Thallus plants, that is to say, the Algæ. At least all the petrified remains which are positively known to be of the primordial period belong exclusively to this class. As all the animal remains of this immense period also belong exclusively to animals that lived in water, we come to the conclusion that at that time organisms adapted to a life on land did not exist at all.
| SYSTEMATIC VIEW | |||||
| Of the Six Branches and Eighteen Classes of the Vegetable Kingdom | |||||
| Primary Groups or Sub-Kingdoms of the Vegetable Kingdom. | Branches or Clades of the Vegetable Kingdom. | Classes of the Vegetable Kingdom. | Systematic Name of the Classes. | ||
| A. Thallus Plants Thallophyta |
| I. Tangles Algæ |
| 1. Primæval algæ | 1. Archephyceæ (Protophyta) |
| 2. Green algæ | 2. Chlorophyceæ (Chloroalgæ) | ||||
| 3. Brown algæ | 3. Phæophyceæ (Fucoideæ) | ||||
| 4. Red algæ | 4. Rhodophyceæ (Florideæ) | ||||
| II. Thread-plants Inophyta |
| 5. Lichens | 5. Lichenes | ||
| 6. Fungi | 6. Fungi | ||||
| B. Prothallus Plants Prothallophyta |
| III. Mosses Muscinæ |
| 7. Tangle-mosses | 7. Charobrya (Characeæ) |
| 8. Liverworts | 8. Thallobrya (Hepaticæ) | ||||
| 9. Frondose-mosses | 9. Phyllobrya (Frondosæ) | ||||
| 10. Turf-mosses | 10. Sphagnobrya (Sphagnaceæ) | ||||
| IV. Ferns Felicinæ |
| 11. Shaft-ferns | 11. Calamariæ (Calamophyta) | ||
| 12. Frondose-ferns | 12. Filices (Pterideæ) | ||||
| 13. Aquatic ferns | 13. Rhizocarpeæ (Hydropterides) | ||||
| 14. Scale-ferns | 14. Selagineæ (Lepidophyta) | ||||
| C. Flowering Plants Phanerogamia |
| V. Plants with Naked Seeds Gymnosperma |
| 15. Palm-ferns | 15. Cycadeæ |
| 16. Pines | 16. Coniferæ | ||||
| VI. Plants with Enclosed Seeds Angiosperma |
| 17. Plants with one seed lobe | 17. Monocotylæ | ||
| 18. Plants with two seed lobes | 18. Dicotylæ | ||||
| PEDIGREE OF VEGETABLE KINGDOM. | |||||
| Gamopetalæ (Flowers with corolla) | |||||
| │ | |||||
| Dialypetalæ (Star-shaped flowers) | |||||
| │ | |||||
| Monochlamydeæ (Flowers with calyx) | Monocotyledonæ (One seed-lobed plants) | ||||
| │ | │ | ||||
| Dicotyledonæ (Two seed-lobed plants) | │ │ │ | ||||
| │ | │ | ||||
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| Cycadeæ (Palm-ferns) | Coniferæ (Pines) | Gnetaceæ | Angiospermæ (Plants with enclosed seeds) | ||
| │ | │ | │ | │ | ||
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| Gymnospermæ (Plants with naked seeds) | |||||
| Selagineæ (Scaled-ferns) | Rhizocarpeæ (Water-ferns) | │ │ │ | Phanerogamæ Flowering plants | Pterideæ (Frondose-ferns) | Calamariæ (Shaft-ferns) |
| │ | │ | │ | │ | │ | │ |
| |||||
| Filicinæ (Ferns) | |||||
| Frondosæ (Leaf-mosses) | Sphagnaceæ (Turf-mosses) | │ │ │ | |||
| │ | │ | │ | |||
| Characeæ (Tangle-mosses) | ||||
| Hepaticæ (Liverworts) | │ │ | ||||
| │ | │ | ||||
| |||||
| Muscinæ (Mosses) | |||||
| Florideæ (Red Algæ) | Fucoideæ (Brown Algæ) | Chlorophyceæ (Green Algæ) | Lichenes (Lichens) | ||
| │ | │ | │ | │ | ||
| │ | ||||
| Algæ (Tangles) | Fungi Inophyta (Thread-plants) | ||||
| │ | │ | ||||
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| Protophyta (Primæval Plants) | |||||
| │ | |||||
| Vegetable Monera | |||||
For these reasons the first and most imperfect of the great provinces or branches of the vegetable kingdom, the division of the Algæ, or Tangles, must be of special interest to us. But, in addition, there is the interest which this group offers when viewed by itself. In spite of the exceedingly simple composition of their constituent cells, which are but little differentiated, the Algæ show an extraordinary variety of different forms. To them belong the simplest and most imperfect of all forms, as well as very highly developed and peculiar forms. The different groups of Algæ are distinguished as much by size of body as by the perfection and variety of their outer form. At the lowest stage we find such species as the minute Protococcus, several hundred thousands of which occupy a space no larger than a pin’s head. At the highest stage we marvel at the gigantic Macrocysts, which attain a length of from 300 to 400 feet, the longest of all forms in the vegetable kingdom. It is possible that a large portion of the coal has been formed out of Algæ. If not for these reasons, yet the Algæ must excite our special attention from the fact that they form the beginning of vegetable life, and contain the original forms of all other groups of plants, supposing that our monophyletic hypothesis of a common origin for all groups of plants is correct. (Compare p. [83.])
Most people living inland can form but a very imperfect idea of this exceedingly interesting branch of the vegetable kingdom, because they know only its proportionately small and simple representatives living in fresh water. The slimy green aquatic filaments and flakes of our pools and ditches and springs, the light green slimy coverings of all kinds of wood which have for any length of time been in contact with water, the yellowish green, frothy, and oozy growths of our village ponds, the green filaments resembling tufts of hair which occur everywhere in fresh water, stagnant and flowing, are for the most part composed of different species of Algæ. Only those who have visited the sea-shore, and wondered at the immense masses of cast-up seaweed, and who, from the rocky coast of the Mediterranean, have seen through the clear blue waters the beautifully-formed and highly-coloured vegetation of Algæ at the bottom, know how to estimate the importance of the class of Algæ. And yet, even these marine Algæ-forests of European shores, so rich in forms, give only a faint idea of the colossal forests of Sargasso in the Atlantic ocean, those immense banks of Algæ, covering a space of about 40,000 square miles—the same which made Columbus, on his voyage of discovery, believe that a continent was near. Similar but far more extensive forests of Algæ grew in the primæval ocean, probably in dense masses, and what countless generations of these archilithic Algæ have died out one after another is attested, among other facts, by the vast thickness of Silurian alum schists in Sweden, the peculiar composition of which proceeds from those masses of submarine Algæ. According to the recently expressed opinion of Frederick Mohr, a geologist of Bonn, even the greater part of our coal seams have arisen out of the accumulated dead bodies of the Algæ forests of the ocean.
Within the branch of the Algæ we distinguish four different classes, each of which is again divided into several orders and families. These again contain a large number of different genera and species. We designate these four classes as Primæval Algæ, or Archephyceæ, Green Algæ, or Chlorophyceæ, Brown Algæ, or Phæophyceæ, and Red Algæ, or Rhodophyceæ.
The first class of Algæ, the Primæval Algæ (Archephyceæ), might also be called primæval plants, because they contain the simplest and most imperfect of all plants, and, among them, those most ancient of all vegetable organisms out of which all other plants have originated. To them therefore belong those most ancient of all vegetable Monera which arose by spontaneous generation in the beginning of the Laurentian period. Further, we have to reckon among them all those vegetable forms of the simplest organization which first developed out of the Monera in the Laurentian period, and which possessed the form of a single plastid. At first the entire body of one of these small primary plants consisted only of a most simple cytod (a plastid without kernel), and afterwards attained the higher form of a simple cell, by the separation of a kernel in the plasma. (Compare above, vol. i. p. [345].) Even at the present day there exist various most simple forms of Algæ which have deviated but little from the original primary plants. Among them are the Algæ of the families Codiolaceæ, Protococcaceæ, Desmidiaceæ, Palmellaceæ, Hydrodictyeæ, and several others. The remarkable group of Phycochromaceæ (Chroococcaceæ and Oscillarineæ) might also be comprised among them, unless we prefer to consider them as an independent tribe of the kingdom Protista.