Source : Webster's Revised Unabridged Dictionary (1913)

Joseph's flower \Jo"seph's flow"er\ (Bot.)
   A composite herb ({Tragopogon pratensis}), of the same genus
   as the salsify.

Sleep-at-noon \Sleep"-at-noon"\, n. (Bot.)
   A plant ({Tragopogon pratensis}) which closes its flowers at
   midday; a kind of goat's beard. --Dr. Prior.

Source : WordNet®

Tragopogon pratensis
     n : weedy European annual with yellow flowers; naturalized in
         United States [syn: {meadow salsify}, {goatsbeard}, {shepherd's
         clock}]