270 LYCOPODIALES [CH. XVIII 



specialised organs of such an extinct genus as Lyginodendron or 

 than in recent plants. Our knowledge of the anatomical structure 

 of many extinct types has already reached a stage when we 

 should take greater heed of the modus operandi of the complex 

 machinery revealed by a study of petrified stems. From the 

 known we proceed to interpret the unknown ; but there is a 

 danger of neglecting the possibilities of evolution during the 

 countless ages which separate the forests of the Coal period from 

 those of the present era. We may easily allow preconceived 

 ideas to warp our judgment in attempting to distribute the 

 manifold activities which made up the life of a Lepidodendron 

 among the structural units of the plant-body. 



