sb. [f. TAP sb.1 + ROOT.] A straight root, of circular section, thick at the top, and tapering to a point, growing directly downwards from the stem and forming the center from which subsidiary rootlets spring.
1601. Holland, Pliny, XVI. xxxi. 477. The Fir and Larch have one tap root and no more; for upon that one maine maister-root they rest and are founded.
1733. Tull, Horse-Hoeing Husb., i. 1. The Tap-Root commonly runs down Single and Perpendicular, reaching sometimes many Fathoms below.
1815. J. Smith, Panorama Sc. & Art, II. 597. Such plants have no tap-roots, but strike their fibres horizontally in the richest part of the soil.
1851. Glenny, Handbk. Fl.-Gard., 160. It has a tap-root like a carrot, but small.
1878. Stevenson, Inland Voy., 77. If the wood grew together like a banyan grove, I would be buried under the tap-root of the whole; my parts should circulate from oak to oak; and my consciousness should be diffused abroad in all the forest, and give a common heart to that assembly of green spires.
fig. 1825. Coleridge, Aids Refl. (1836), 349. Its fibres are to be traced to the tap-root of humanity.
1887. Lowell, Democr., 36. This sentiment, which is the very tap-root of civilization and progress.
attrib. 1890. Eng. Illustr. Mag., Christm. No. 158. That’s a tap-root idea, Fraser.
Hence Tap-root v. intr., of a plant, to send down a tap-root (whence Tap-rooting ppl. a.); Tap-rooted a., having a tap-root.
1725. Bradley’s Fam. Dict., s.v. Ilex, These, like our English Oak, are tap-rooted, and therefore delight in deep Soil.
1769. L. Edward, in Hist. Linc. (1834), I. 20. The oak roots stand upon the sand, and tap-root into the clay.
1805. R. W. Dickson, Pract. Agric., I. 12. In loosening the ground for carrots, or other tap-rooted plants.
1871. W. Sutherland, Hand-bk. Flowers, 148. It [Morina longifolia] flourishes best in light rich loam of considerable depth, being a deep tap-rooting plant.
1897. Willis, Flower. Pl., I. 185. Tap-rooting plants … would not be able to cling to their supports in time to prevent falling off.
