THE plants belonging to the Class Algæ grow in water, either in that of the sea or in fresh water; a few of them, however, being found on damp earth, damp walls, &c. The marine Algæ are commonly known as sea-weeds; but the fresh-water Algæ generally receive but little popular notice, forming, as they do, slimy masses or strata, of a green or brownish, sometimes red, colour.
Algæ are of simple structure, consisting entirely of cells; in some these are single, in others, united end to end, to form threads or filaments, or grouped into a leaf-like expansion, or collected few together into a little spherical group or a flat plate. They possess none of the fibres, vessels, or ducts of the higher plants, although some long and slender cells, existing in the stalks of the fronds of the larger kinds, bear considerable resemblance to woody fibre. They exhibit no distinction of stem and leaf, but consist of fronds representing the stem and leaf combined and undistinguishable. And the term frond must be understood to signify the separate parts arising from the point of attachment when they are fixed; and in the case of those which are unattached or free, the entire plant is called a frond.
The Algæ are divided into three Orders, viz. the Fucoid´eæ or olive-coloured Algæ, the Florid´eæ or red, and the Confervoid´eæ or green Algæ.
Fucoid´eæ, Fucoid Algæ, or Melanospor´eæ (μἑλας, black or dark). The plants composing this order form our largest sea-weeds, and are found everywhere in the sea and on the sea-shore. They are of an olive-green or olive-brown colour, and usually become darker on drying.
| PLATE IV. [[PAGE 64.]] | |
| Marine Algæ. | |
| Fig. | |
| 1. | Dasya coccinea, piece of. |
| 2. | Dasya coccinea, portion with capsule (ceramidium). |
| 3. | Dasya coccinea, portion of main filament. |
| 4. | Dasya coccinea, section of filament. |
| 5. | Melobesia polymorpha. |
| 6. | Melobesia polymorpha, portion with capsules (ceramidia). |
| 7. | Jania rubens. |
| 8. | Jania rubens. |
| 9. | Lithocystis Allmanni. |
| 10. | Ceramium nodosum. |
| 11. | Ceramium nodosum, filament. |
| 12. | Ceramium rubrum, filament. |
| 13. | Ceramium rubrum, tetraspore. |
| 14. | Ceramium rubrum, end of filament. |
| 15. | Ceramium rubrum, capsule (favella). |
| 16. | Fucus vesiculosus, receptacles of. |
| 17. | Fucus vesiculosus, capsules (conceptacles). |
| 18. | Fucus serratus, antheridial conceptacles. |
| 19. | Spore of Fucus vesiculosus. |
| 20. | Antheridia of Fucus serratus. |
| 21. | Plocamium coccineum, sporophyll. |
| 22. | Plocamium coccineum, with capsule (coccidium). |
| 23. | Plocamium coccineum, portion of frond. |
| 24. | Plocamium coccineum, tetraspore from sporophyll. |
| 25. | Polysiphonia fastigiata, portion of. |
| 26. | Polysiphonia fastigiata, filament with capsules (ceramidia). |
| 27. | Polysiphonia fastigiata, portion of filament. |
| 28. | Corallina officinalis. |
| 29. | Corallina officinalis, portion of filament. |
| 30. | Corallina officinalis, capsule (ceramidium). |
| 31. | Enteromorpha compressa. |
| 32. | Enteromorpha compressa, cells of frond. |
| 33. | Hypnea purpurascens, capsule (coccidium). |
| 34. | Hypnea purpurascens, spores. |
| 35. | Hypnea purpurascens, filament. |
