75. Fleshy roots may be single or multiple. The single root of the commoner biennials is the primary root, or tap-root, which begins to thicken in the seedling. Names are given to its shapes, such as
Conical, when it thickens most at the crown, or where it joins the stem, and tapers regularly downwards to a point, as in the Parsnip and Carrot (Fig. [84]);
Turnip-shaped or napiform, when greatly thickened above, but abruptly becoming slender below; as the Turnip (Fig. [83]); and
Spindle-shaped, or Fusiform, when thickest in the middle and tapering to both ends; as the common Radish (Fig. [85]).
76. These examples are of primary roots. It will be seen that turnips, carrots, and the like, are not pure root throughout; for the caulicle, from the lower end of which the root grew, partakes of the thickening, perhaps also some joints of stem above: so the bud-bearing and growing top is stem.
Fig. 86. Sweet-Potato plant forming thickened roots. Some in the middle are just beginning to thicken; one at the left has grown more; one at the right is still larger.
Fig. 87. Fascicled fusiform roots of a Dahlia: a, a, buds on base of stem.