Algae

“ There is left for us a numerous and varied array of algae, representing several lines of ascent, all tending to diverge from one another. But these forms have some important points in common, particularly as concerns certain events in their life histories. There is immense variety in the form of the plant body which ranges from a single cell to structures with stalks and leaf-like organs. ”

“ The bed of the ocean, from the tiny lakelets left by the retiring tide to the greatest depths ever reached by trawl and dredge, is found to be teeming with exquisite forms of life. Delicate plant-like forms are found clinging to rocks and shells, or spreading themselves over the broad fronds of the algae. Every peculiarity of vegetation is mimicked; graceful stems rising from tangled roots send out branches which bear raceme-like clusters of buds, and delicate bells whose beauty no words can describe.
Fig. 5.—Roving Medusa of Tubularia indivisa. ”

“ Before discussing our knowledge, or rather lack of knowledge, of fossil algae at greater length, it will be well to briefly consider the manner of occurrence and botanical nature of existing forms. In the sea and in fresh water, as well as in damp places and even in situations subject to periods of drought, algae occur in abundance in all parts of the world. ”

“ A green plant can take raw material like earth, air and water and, with the aid of sunlight, make its own food. Algae are found in oceans, rivers, lakes, ponds, marshes and warm springs, everywhere. Some of them are very beautiful, in a great variety of forms and colors. The very commonest algae that you can all find, almost everywhere, is the green scum that forms on quiet ponds and swamps. Scum is all broken up into single plants, or knots andstrings of cells, and can be easily separated and studied under a microscope. ”

“ Each class of flowerless or cryptogamic plants requires special treatment for the herbarium.
Marine algae are usually mounted on tough smooth white cartridge paper in the following manner. Growing specimens of good colour and in fruit are if possible selected, and cleansed as much as practicable from adhering foreign particles, either in the sea or a rocky pool. Some species rapidly change colour, and cause the decay of any others with which they come in contact. ”

“ Most of the simple algae are annual, their life enduring only for part of the year; the branching algae are more often perennial, but in their cases not only are observations as to duration lacking, but however simply we may use the term individual, its application is difficult. The larger terrestrial plants with woody tissues which we denote roughly as shrubs and trees have an individuality which, although different from that of a hyacinth or carrot, is usually obvious. ”

“ In the case of the freshwater algae, however, belonging to the Chlorophyceae and Cyanophyceae, although they required to be immersed during the vegetative period, the reproductive cells are often capable of resisting a considerable Habitat.degree of desiccation, and in this condition are dispersed through great distances by various agencies. Again, as is well known, many species of marine algae growing in the region between the limits of high and low water are so constituted that they are exposed to the air twice a day without injury. ”

“ Several genera live as endophytes in the tissues of other algae. The recent species of this section of algae are characteristic of temperate and tropical seas. One subdivision of the red algae, the Corallinaceae, is extremely important from a geological point of view and must be dealt with in some detail. ”

“ No class of plants is more interesting than the Algae. Notwithstanding their very simple structure, they offer every variety of shape, size, and color. While many of them are very minute, the beauty of their form, the delicacy of their structure, and their exquisite coloring, never have failed to attract the attention of the microscopist. The Confervoidae, or green Algae, are widely distributed, every pond, ditch, spring, and stream having representatives. ”

“ From the beginning he had a shrewd perception of what lay within his reach, and what was beyond it. "The extent to which I mean to go in botany," he wrote at twenty-one years, "is to know British plants of all kinds as well as possible; to know Algae of all countries specially well; to collect all foreign Cryptogamia that may fall in my way, and to know them moderately well.... My reason for choosing the Algae is pure compassion; they being sadly neglected by the present generation, though at a former time they were in high favour." ”

“ The great majority of the aquatic algae, both freshwater and marine, are attached plants. Some, however, are wanderers, either swimming actively with the aid of cilia, or floating inertly as the result of a specific weight closely approaching that of the medium. ”

“ The elaborate provision for the conduct of water from part to part which has played so important a rôle in the morphological development of land plants is entirely wanting in algae, such conducting tissues as do exist in the larger Phaeophyceae and Rhodophyceae serving rather for the convection of elaborated organic substance, and being thus comparable with the phloem of the higher plants. ”

“ The evolution of the algae has led for the most part to the development and long continuance of such phases of the life history as are stationary, and from these the filamentous, membranous and otherwise differentiated plant bodies have arisen. ”

“ The great majority of algae, however, grow like land-plants attached to a substratum, and to these the term benthos is now generally applied. While the root of land-plants serves for the double purpose of attachment and the supply of water, it is attachment only that is usually sought in the case of algae. ”

“ Evidently the oxygen thrown off by the alga is precisely what the plant needs, and the carbonic acid and nitrogenous waste eliminated by the animal is most useful to the alga. Moreover, the algae gain the advantage of ready locomotion with their host, and the animal can go further into unfavorable media when stocked with algae ready to build up starches and sugary matters from carbonic acid and water. ”

“ I wish to recall to the inquirer that here on our own globe the spores of the algae and other plants of that order have the power of swimming freely in the sea. Still, they are plants—plants just as mobile as fishes. They become stationary only at a later stage of their development. ”

“ Many of the fresh-water algae which form a mere crust, such as Palmella cruenta, may be placed in a vessel of water, where after a time they float like a scum, the earthy matter settling down to the bottom, and may then be mounted by slipping a piece of mica under them and allowing it to dry. ”

“ Certainly the plants were in the ascendency. The mobile green Algae were characteristic of the time. It is a remarkable thing that though they are probably the progenitors of all that [Pg 19] vast world of vegetable life which enriches the world today, the Algae have always gone on reproducing their own kind. Today we can watch, under a microscope, the activities of the first form of terrestrial life, born incalculable aeons ago. ”

“ These algae are a genuine prodigy of creation, one of the wonders of world flora. This family produces both the biggest and smallest vegetables in the world. Because, just as 40,000 near–invisible buds have been counted in one five–square–millimeter space, so also have fucus plants been gathered that were over 500 meters long!
We had been gone from the Nautilus for about an hour and a half. It was almost noon. I spotted this fact in the perpendicularity of the sun's rays, which were no longer refracted. ”

“ Algae: simple plants without differentiated vascular systems. They range from the slime-like single celled plants often seen on the surfaces of stagnant water and wet soil, to seaweeds many metres in length. ”

“ With the mobile algae, separation of the members of each generation is the rule, unless the individuals come to be associated in a thallus, or are grouped in contact with the substratum. Flowering plants that are relatively immobile, especially in the seed state, drop their seeds beneath and about the parent plants, and in consequence dense association of the new plants is the rule. ”

“ In comparison with the higher plants, algae exhibit so much simplicity of structure, while the conditions under which they grow are so much more readily controlled, that they have frequently been the subject of physiological investigation with a view chiefly to the application of the results to the study of the higher plants. ”

“ The statement is occasionally made that the numerous fossil algae and the absence of higher plants in the older strata justify the description of the oldest rocks as belonging to the ‘age of algae.’ Such an assertion rests on an unsound basis, and is rather the expression of what might be expected than what has been proved to be the case. The oldest plants with which we are at all closely acquainted are of such a type as to forcibly suggest that in the lowest fossiliferous rocks we are still very far from the sediments of that age which witnessed the dawn of plant life. ”

“ It arises from the fact that algae, as generally understood, do not constitute a homogeneous group, suggesting a descent from a common stock. Among them there exist, as will be seen hereafter, many well-marked but isolated natural groups, and their inclusion in the larger group is generally felt to be a matter of convenience rather than the expression of a belief in their close inter-relationship. ”

“ However, since algae are a relatively complex form of life, life in some simpler form could have originated much earlier. Organic material similar to that found in modern organisms can be detected in these ancient deposits as well as in much older Precambrian rocks. ”

“ Often there are so many algae plants on the gray net surface of a lichen, that they turn it to a soft sage green color, very bright and moist. The algae being green, collect food from the sun and air and feed the lichen, and the lichen covers the algae with a network of gray thread cells to keep it from getting too dry.
Nature makes many partnerships between plants and animals that can help each other. Bees and butterflies help the flowers grow seeds. Men help plants to grow, and make friends of horses and dogs. ”

“ Stated briefly, my conclusion is that the algae of the 183French authors may be definite organic bodies, but it is unwise to attempt to determine their affinities within such narrow limits as have been referred to in the above résumé. The structure of the bituminous deposits is worthy of careful study, and it is by no means impossible that further research might lead us to accept the view of the earlier investigators, that the brightly coloured organic-like bodies may be inorganic in origin. ”

“ He was able also to prove that this gas came from the associated algæ—specimens destitute of algæ giving off no oxygen whatever.
It is, therefore, now very certain that the yellow cells of radiolarians and the pigment-bodies of cœlenterates are in many cases true alga; living in the animal substance. ”

“ If these algae were to live, they had to jump from swimming tad-pole seaweeds into—not quite, but almost into froggy mosses with legs, and air-breathing lungs. They became those curious plants that we know as liver-worts. Like frogs they can live only in wet places ”

“ Lastly, there are blue-green Algae, jelly-like masses found on trees, rocks, damp earth or floating as green slimes in fresh water. Most water plants are active and independent. They are on the upward road, for though they have not distinct stems, roots, leaves or fruit, their different parts, as I have already said, show a decided likeness to these, especially their “holdfasts” to roots and their air-bladders to fruit. The exquisite red seaweeds are as graceful in form and vivid in color as many flowers. ”

“ The comprehensive generic name Algites [245] has been suggested as a convenient designation for impressions or casts which are probably those of algae.
SUPPOSED FOSSIL ALGAE.
Some of the fossils described by Mr Kidston from British Carboniferous rocks as probably algae present an undoubted algal appearance, and might be placed in the genus Algites; but in some cases—e.g. Chondrites plumosa [246] Kidst. from the Calciferous Sandstone of Eskdale, one feels much more doubtful; in this particular instance the impressions suggest the fine roots of a water-plant. ”

“ The sources of material for examination are manifold. A large number of the Blue-green Algae are found throughout the year in places, where there is a constant flow of water, such as drains and water-courses. ”

“ Then, and still more briefly, have we stopped to see those less known plants that produce no flowers, such as the ferns, mosses, fungi, and finally the seaweeds or algæ. These are all to be considered as the ancestors of flowering plants, the ferns the nearest to them and the algæ probably the most distant relatives. The development of plants from the minutest alga up to our most gorgeous flowering plant, is an infinitely slow and painful process. ”

“ The plants are very minute members of the almost universal algae family which are among the most primitive forms of life on earth. They are able to extract the nourishment they require from the surface of a glacier as it melts slightly under the glare of the Arctic sun. ”