. Botany for academies and colleges: consisting of plant development and structure from seaweed to clematis. Botany; 1889. 24 ACADEMIC BOTANY. tary, as in Navicula (Fig. 13, A). Each cell here also is an individual. In different genera the cells are of different shapes,ânow like a rod (whence the name BaoUlaria, Little Stick), now like a buckler (Fig. 14), now like a boat; this last getting its botanical nameâNavicula (Little Boat)â from its shape. The cell is called Frmtule (fragment), be- cause at maturity the cells separate from one another as if broken at the joints or points of union. Eac
. Botany for academies and colleges: consisting of plant development and structure from seaweed to clematis. Botany; 1889. 24 ACADEMIC BOTANY. tary, as in Navicula (Fig. 13, A). Each cell here also is an individual. In different genera the cells are of different shapes,ânow like a rod (whence the name BaoUlaria, Little Stick), now like a buckler (Fig. 14), now like a boat; this last getting its botanical nameâNavicula (Little Boat)â from its shape. The cell is called Frmtule (fragment), be- cause at maturity the cells separate from one another as if broken at the joints or points of union. Each frustule is two-valved; it imbibes silex, or silica (flint, quartz), so that the protoplasm is invested with a shell. A drop of water contains millions of these tiny things; when magni- fied twenty diameters they are still invisible. Yet the silica protects them, so that they are nearly in- destructible. They live, dried, a hundred years; then, when borne to the water, or to a moist place, they begin active life again. Their motions are wonderful. The Little Boats (Fig. 13, A) move regularly back and forth as if propelled by an unseen oarsman with invisible oars. And so they are; the protoplasm sends them to and fro in search of food; and so powerful is its attraction that the fine grains of sand which furnish the silica of the outer wall of the boat flock to it and run hither and thither along its sides as if they too were alive. Un- _ der the cities of Kichmond and Peters- burg, Virginia, there is a deposit of their fossil remains twenty feet thick. A cubic inch contains forty trillions ; yet each tiny shell is carved with ex- â/'?â M-âA, G^â¢ammotop*oramartIla; '^ . .. â rm. T» Stoningtou, Conn.; gait-water. B, quisite tracery. The Kotten-stone, or meUtira sulcata; a, frustule; Bich- TripolijOf our household economy owes mond, Va. o, AciinoptjieimB smariut, its polishing qualities to the shells of BichmoDd, Va. B and C are fossils, myriads of fossil diatom
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