SEA-Plants. Count Marfigli, who was at indefatigable pains to collect the various sea-plants of several places, divides all those productions into three classes.
The first class contains the soft or herbaceous ones; the second the ligneous ones, or such as are of a woody hardness; and the third, those which are of the hardness of stone. Of the first class are the algae, called sea-wrack; the fucuses, or sea-oaks; the sea-mosses, or conservas; and the different species of sponges.
Of the second kind are those called lytophyta by the ancients, as if their hardness approached to that of stones. All these consist of two substances, a cortical and an internal. The cortical part, while in the sea, is soft; but in drying, it becomes as hard as chalk, or thereabouts, easily crumbling to pieces between the fingers: this is what deceived the ancients into an opinion of its being of a stony nature. The internal substance, properly speaking, seems to have more the nature of horn than of wood: if it is burnt, it throws out a spume or froth, like that which horns or feathers of animals yield in the fire, and their smell in burning is of the same kind. The branches of these plants are very pliable, bending in the manner of whalebone; and they give the same resistance to a knife in the cutting.
The stony plants, which should properly be called the lytophyta, but which never are called so, are the
several species of coral, madrepora, and the like. The madrepora differs from the coral, in having its surface pierced with almost innumerable holes. The corals, however, are now discovered to belong to the animal, not the vegetable kingdom. See CORAL.
The algas are the only sea-plants which have any roots, properly so called; these therefore grow out of the soft bottom of the sea as other plants out of the earth: but all the other sea-plants, without exception, appear fixed upon hard and solid bodies, incapable of affording them any nourishment; such as stones, shells, pieces of iron, of wood, &c. and sometimes on other plants; and they are not fastened to these substances by fibres passing into or surrounding them, but merely by a foot or pediment, capable of only fixing them down, not of drawing nourishment from the substances, were there any there. From this observation, the author concludes, that all the plants which have no roots, may be properly said to be all root, or to perform the office of roots in their whole substance, or that they take in nourishment in every part by certain pores, which in many are visible, and cover the whole surface.
This manner of receiving nourishment, he also observes, very well suits their condition, since they are always surrounded on all sides with that water by which they are to be nourished; whereas the plants which grow on land have only a part of them buried in the earth, from whence they are to be supplied with the proper juices. The roots of land-plants, therefore, have only the necessary organs for receiving supplies; whereas the sea-plants, he finds to be all over covered with small glandules, whose office it is to receive and to convey into the internal parts of the plant the proper juices for its nourishment; and these, he observes, are in general of a glutinous and milky nature. The great difference between the land and sea plants is seen in this familiar instance: A land-plant will remain fresh for a long time in all its parts, on one end of the stalk only being plunged in water; but a sea-plant, if part of it be out of water and part in, will always be fresh and vigorous in that part which is under water, while the part that is dry will wither and decay. It is easy hence to see, that the several parts of the land-plants have connections with and dependences on one another; whereas, in the sea-plant, every part takes in its own nourishment, and lives and flourishes wholly independent of the rest.
After having gone through this general system, the author descends to several remarkable particulars. He mentions an instance of a fucus, whose stalk, when in its growing state, is a quarter of an inch in diameter; yet in drying shrinks up so much, as to be not thicker than a single thread. Another species, called by the fishermen the sea-orange, from its resemblance to an orange in shape, he observes, is properly a fucus; it has neither stalk nor branches, but consists wholly of this globular body; it is not a solid substance, but a membrane of about one ninth of an inch in thickness, regularly distended into this shape by being filled with sea-water. All over the sides of this cavity there are fixed slender filaments, which traverse the whole, and probably receive nourishment from the water contained in the cavity, and distribute it to the several parts of the sides where they are inserted. Another sea-plant
this author mentions, only appears in the shape of a bark; it affixes itself to the branches of the lythophyta, when they have lost their natural bark, and sometimes in the same manner coats and crusts over the surface of stones. When it is fresh, it is of a lively red, of the consistency of a mushroom, and about the thickness of the back of a common knife; and its external surface is full of small prominences, which contain a glutinous juice; round about these also there stand several yellow tubercles, which, with the red of the ground of the plant, make upon the whole a very beautiful appearance. Its under-surface is perfectly smooth and glossy. This seems a much more remarkable plant, as to the manner of its vegetation, than those which grow on other plants at land.