The Collaborative International Dictionary of English v.0.48:

Paleobotany \Pa`le*o*bot"a*ny\, n. [Paleo- + botany.]
   That branch of paleontology which treats of fossil plants.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Phytolithology \Phy`to*li*thol"o*gy\, n. [Phyto- + lithology.]
   The branch of science which treats of fossil plants; --
   usually called paleobotany, sometimes paleophytology.
   [1913 Webster]

WordNet (r) 3.0 (2006):

paleobotany
    n 1: the study of fossil plants [syn: paleobotany,
         palaeobotany]