The Collaborative International Dictionary of English v.0.48:

Spearmint \Spear"mint`\, n. [So named from its spiry, not
   capitate, inflorescence. --Dr. Prior.] (Bot.)
   A species of mint (Mentha viridis) growing in moist soil.
   It vields an aromatic oil. See Mint, and Mentha.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mint \Mint\ (m[i^]nt), n. [AS. minte, fr. L. mentha, Gr. mi`nqa,
   mi`nqh.] (Bot.)
   The name of several aromatic labiate plants, mostly of the
   genus Mentha, yielding odoriferous essential oils by
   distillation. See Mentha.
   [1913 Webster]

   Note:

   Corn mint is Mentha arvensis.

   Horsemint is Mentha sylvestris, and in the United States
      Monarda punctata, which differs from the true mints in
      several respects.

   Mountain mint is any species of the related genus
      Pycnanthemum, common in North America.

   Peppermint is Mentha piperita.

   Spearmint is Mentha viridis.

   Water mint is Mentha aquatica.
      [1913 Webster]

   Mint camphor. (Chem.) See Menthol.

   Mint julep. See Julep.

   Mint sauce, a sauce flavored with spearmint, for meats.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Yerba \Yer"ba\, n. [Sp.] (Bot.)
   An herb; a plant.
   [1913 Webster]

   Note: This word is much used in compound names of plants in
         Spanish; as, yerba buena [Sp., a good herb], a name
         applied in Spain to several kinds of mint (Mentha
         sativa, Mentha viridis, etc.), but in California
         universally applied to a common, sweet-scented labiate
         plant (Micromeria Douglasii).
         [1913 Webster]

   Yerba dol osa. [Sp., herb of the she-bear.] A kind of
      buckthorn (Rhamnus Californica).

   Yerba mansa. [Sp., a mild herb, soft herb.] A plant
      (Anemopsis Californica) with a pungent, aromatic
      rootstock, used medicinally by the Mexicans and the
      Indians.

   Yerba reuma. [Cf. Sp. reuma rheum, rheumatism.] A low
      California undershrub (Frankenia grandifolia).
      [1913 Webster]