The Collaborative International Dictionary of English v.0.48:

Phyton \Phy"ton\, n.; pl. Phytons. [NL., fr. Gr. fyto`n
   plant.] (Bot.)
   One of the parts which by their repetition make up a
   flowering plant, each being a single joint of a stem with its
   leaf or leaves; a phytomer.
   [1913 Webster]