. The power of movement in plants . Plants; Botany. iO CIBCUMNUTATION OP SEEDLINGS. Chap. L Fig. 29. pressed alternately with greater and less force on them. There must, therefore, have been movement in at least two planes at right angles to one another. These radicles were so delicate that they rarely had the power to sweep the glasses quite clean. One of them had developed some lateral or secondary rootlets, which projected a few degrees beneath the horizon; and it is an im- portant fact that three of them left distinctly serpentine tracks on the smoked surface, showing beyond doubt that the
. The power of movement in plants . Plants; Botany. iO CIBCUMNUTATION OP SEEDLINGS. Chap. L Fig. 29. pressed alternately with greater and less force on them. There must, therefore, have been movement in at least two planes at right angles to one another. These radicles were so delicate that they rarely had the power to sweep the glasses quite clean. One of them had developed some lateral or secondary rootlets, which projected a few degrees beneath the horizon; and it is an im- portant fact that three of them left distinctly serpentine tracks on the smoked surface, showing beyond doubt that they had circumnutated like the main or primary radicle. But the tracks were SD slight that they could not be traced and copied after the smoked surface had been varnished. Hypricotyl.—A seed lying on damp sand was firmly fixed by two crossed wires and by its own growing radicle. The cotyle- dons were still enclosed within the seed-coats; and the short hypocotyl, between the summit of the radicle and the cotyledons, was as yet only slightly arched. A filament (-85 of inch in length) was attached at an angle of 35° above the horizon to the side of the arch adjoining the cotyle- dons. This part would ultimately form the upper end of the hypo- cotyl, after it had grown straight and vertical. Had the seed been properly planted, the hypocotyl at this stage of growth would have been deeply buried beneath the surface. The course followed by the bead of the filament is shown in Fig. 28. The chief lines of movement from left to right in the fiigure were parallel to the plane of the two united cotyledons and of the flattened seed; and tliis movement would aid in dragging them out of the seed-coats, which are held down by a special struc- ture hereafter to be described. The movement at right angles to the above lines was due to the arched hypocotyl becoming more arched as it increased in height. The foregoing observa- tions apply to the leg of the arch next to the cotyledons, but. Cucurbi
Size: 1339px × 1867px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectbotany, booksubjectplants, bookyear18
