The Collaborative International Dictionary of English v.0.48:

Tylosis \Ty*lo"sis\, n.; pl. Tyloses. [NL., fr. Gr. ty`los a
   lump, knot.] (Bot.)
   An intrusion of one vegetable cell into the cavity of
   another, sometimes forming there an irregular mass of cells.
   --Goodale.
   [1913 Webster]