The group has until recent years been regarded as comprising three classes distinguished by well-marked physiological featuresthe Algae (including the Seaweeds) which contain chlorophyll, the Fungi which have no chlorophyll and therefore lead a saprophytic or parasitic mode of life, and the Lichens which are composite organisms consisting of an alga and a fungus living together in a mutual parasitism (symbiosis); Bacteria were regarded as a section of Fungi.
Symbiosis.Though green plants thus possess a very complete mechanism for the manufacture of their different foodstuffs, it is not always exercised to the fullest extent.
Such a relationship is known as symbiosis, and the large majority of the cases of so-called parasitism among green plants can be referred to it.
The union taking place underground, while the bulk of both partners in the symbiosis rises into the air, renders the association a little difficult to see, but there is no doubt that the plants in question do afford each other assistance, forming, as it were, a kind of partnership. The most pronounced case of parasitism, that of Cuscuta, the dodder, which infests particularly clover fields, appears to differ only in degree from those mentioned, for the plant, bare of leaves as it is yet contair.s a little chlorophyll.
Many other cases of symbiosis have been investigated with some completeness, especially those in which lower plants than the Phanerogams are concerned.
The discovery of the widespread occurrence of this mycorhizal symbiosis must be neld to be one of the most important results of research upon the nutritive processes of plants during the closing decade of the 19th century.
Each species of green plant may form a mycorhiza with two or three different Fungi, and a single species of Fungus may enter into symbiosis with several green plants.
The importance of the symbiosis can only be understood by considering the relationship in which plants stand with regard to the free nitrogen of the air.
This peculiar relationship suggests at once a symbiosis, the Fungus gaining its nutriment mainly or entirely from the green plant, while the latter in some way or other is able to utilize the free nitrogen of;he air.
393; and Symbiosis, Ann.
It now is - whether the free nitrogen of the atmosphere is brought into combination under the influence of micro-organisms, or other low forms, either within the soil or in symbiosis with a higher plant, thus serving indirectly as a source of nitrogen to plants of a higher order.
For 50o years Austria had fulfilled this double task fairly adequately; but in its third task, that of turning a mechanical combination into an intimate union, a symbiosis of the nationalities, the State failed.
An association of two organisms to their mutual advantage is known as symbiosis, and the lichen in botanical language is described as a symbiotic union of an alga and a fungus.
The relation of the fungus to the alga, though it may be described in general terms as one of symbiosis, partakes also somewhat of the nature of parasitism.
It must be borne in mind that the exact nutritive relations of the two constituents of the lichen have not been completely elucidated, and that it is very difficult to draw the line between symbiosis and parasitism.
Aspergillus Oryzae plays an important part in saccharifying the starch of rice, maize, &c., by means of the abundant diastase it secretes, and, in symbiosis with a yeast which ferments the sugar formed, has long been used by the Japanese for the preparation of the alcoholic liquor sake.
Since then numerous other cases of symbiosis have been demonstrated.
Numerous other cases of symbiosis have been discovered among the fungi of fermentation, of which those between Aspergillus and yeast in sake manufacture, and between yeasts and bacteria in kephir and in the ginger-beer plant are best worked out.
For cases of symbiosis see Bacteriology.
Symbiosis: Ward, "The Ginger-Beer Plant," Phil.
Soc. (1892); "Symbiosis," Ann.
This interesting case of symbiosis is equalled by yet another case.
The work of numerous observers has shown that the free nitrogen of the atmosphere is brought into combination in the soil in the nodules filled with bacteria on the roots of Leguminosae, and since these nodules are the morphological expression of a symbiosis between the higher plant and the bacteria, there is evidently here a case similar to the last.
We have here a very interesting case of symbiosis as mentioned above.
19, 20), where anaerobic bacteria are associated with yeasts, several interesting examples of symbiosis among bacteria are now known.
Symbiosis: Marshall Ward, " Symbiosis," Ann.