18 PAL^ONTOLOGICAL BOTANY. 



surface of tlie wood is the end of the fibres, the section 

 being transverse. 



This polisher must be turned quite flat and smoothed by 

 a plane, as the willow, from its softness, is peculiarly difficult 

 to turn. It is also of consequence to remark that both sides 

 should be turned, so that the lap, when dry, is quite parallel. 

 This lap is most conveniently adapted to the common face 

 chuck of a lathe with a conical screw, so that either surface 

 may be used. This is made evident, when we state that this 

 polisher is always used moist, and, to keep both surfaces 

 parallel, must be entirely plunged in water before using, as 

 both surfaces must be equally moist, otherwise the dry surface 

 will be concave and the moist one convex. The polishing 

 substance used with this lap is putty powder (oxide of tin), 

 which ought to be well washed, to free it from grit. The 

 calcareous fossils being finely ground, are speedily polished 

 by this method. To polish softer substances, a piece of cloth 

 may be spread over the wooden lap, and finely-levigated 

 chalk used as a polishing medium. 



In order to study fossil plants well, there must be an 

 acquaintance with systematic botany, a knowledge of the 

 microscopical structure of all the organs of plants, such as 

 their roots, stems, barks, leaves, fronds, and fi'uit; of the 

 markings which they exhibit on their different surfaces, and 

 of the scars which some of them leave when they decay. It 

 is only thus we can expect to determine accurately the living 

 affinities of the fossil. Brongniai't says, that before compar- 

 ing a fossil vegetable with living plants, it is necessary to 

 reconstruct as completely as possible the portion of the plant 

 under examination, to determine the relations of these por- 

 tions to the other organs of the same plant, and to complete 

 the plant if possible, by seeing whether, in the fossils of the 

 same locality, there may not be some which belong to the 

 same plant. The connection of the different parts of the 



