The Collaborative International Dictionary of English v.0.48:

Lactescent \Lac*tes"cent\, a. [L. lactescens, p. pr. of
   lactescere to turn to milk, incho. fr. lactere to be milky,
   fr. lac, lactis, milk: cf. F. lactescent.]
   1. Having a milky look; becoming milky. [Obs.]
      [1913 Webster]

   2. (Bot.) Producing milk or a milklike juice or fluid, as the
      milkweed. See Latex.
      [1913 Webster]