The Collaborative International Dictionary of English v.0.48:

Silvas \Sil"vas\or Selvas \Sel"vas\, n. pl. [L. silva a forest,
   Sp. selva.]
   Vast woodland plains of South America.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Silva \Sil"va\, n.; pl. E. Silvas, L. Silvae. [L., properly,
   a wood, forest.] [Written also sylva.] (Bot.)
   (a) The forest trees of a region or country, considered
       collectively.
   (b) A description or history of the forest trees of a
       country.
       [1913 Webster]