56 STUDY OF COMMON PLANTS. 



condensed into such a summary statement as the. fore- 

 going ; but it will at least serve to point out the important 

 parts played by the various elements of the stem as they 

 contribute, each its share, to the vrork of the whole. The 

 mechanical system is treated at length by Haberlandt, 

 Physiologische Pflanzenanatomie, pp. 96-143, and an ex- 

 tended review of the theories regarding the ascent of 

 water in the trunks of tall trees is given . by ll. Marshall 

 Ward, Timber and Some of its Diseases, Chap. IV, 



