The Mexican or Vera Cruz sarsaparilla is derived from this species. ... [The roots] consist of a head or caudex with numerous long radicles, which, however, are somewhat smaller than in that variety, and have a thinner bark. They are often also much coiled with earth. It contains but little starch and has quadrangular endodermal cells, with thickened walls, and more or less oval lumen.

Source: United States Dispensatory (1918) ^[3]

Powdered Sarsaparilla is light grayish-brown to dark grayish-brown; when examined under the microscope it exhibits numerous starch grains, from 0.003 to 0.023 mm. in diameter, spherical, or biconvex or spherical-tetrahedral, single to 2- to 4-compound, and frequently with a central-elliptical cleft; calcium oxalate in raphides, from 0.006 to 0.035 mm. in diameter, occurring singly or in groups; cells of the hypodermis and endodermis with lemon-yellow or reddish-yellow porous walls and, in the case of Mexican Sarsaparilla, showing an uneven or irregular thickening, the individual cells from 0.08 to 0.5 mm. in length; fragments of trachea) with simple and bordered pores or scalariform or reticulate thickenings associated with sclerenchymatous fibers having rather thin, very slightly lignified and porous walls.

Source: United States Dispensatory (1918) ^[6]