1902] RISE OF THE TRANSPIRATION STREAM 267 



1902 classing this with the work of Pitra, Bohm (1892), and C. 

 Kraus. Looked at in this way, we have here a complete layer 

 of live cells formed across the water conducting tissues, making 

 still another osmometer "" — an enormous nectary. The water 

 being drawn into this nectary from the conducting elements by 

 osmosis, it is exactly the same, so far as concerns the problem of 

 the ascent of the water, as though it were drawn by the same 

 force into the transpiring cells of the leaf. 



Strasburger, who can speak with most authority, says the 

 structure of many trees, notably Dracaena (1893:17), is much 

 less favorable to the action of living cells than is that of gym- 

 nosperms, which were Godlewski's chief subject of discussion. 



The most conclusive argument against the activity of liv- 

 ing cells in the ascent of sap is its moving freely upward in stems 

 where the cells have been killed by poisons or by boiling. More 

 or less injurious stains have always been used to detect the path 

 of the transpiration stream. Of more violent poisons, KgFe 

 CNg was carried up in experiments for the same purpose by 

 Rominger, Hoffmann (1848; 1850 : 796,842), Von Mohl (1851 : 

 23i),andVanTieghem (118 seq.) Boucherie (1840), in experi- 

 ments in which the poisons must have risen more than lo'", had 

 various ones absorbed, especially iron pyrolignite. This was also 

 carried up more than forty feet in an experiment already described 

 by T. Hartig (1853 :3I3), and was afterward carried downward 

 in a reversed transpiration current in an experiment by the same 

 author(i86i : 23). Saussure (1804) let CuSO^ be absorbed, 

 which killed the plants after a few days. Dutrochet (1837: 214) 

 found that H^SO^ strong enough to discolor them would rise 

 in stems; from which he did not fail to conclude that living 

 cells were unnecessary to its movement. Strasburger's work on 

 the conduction of poisons culminated with an experiment (1893 : 

 10-17; other work, 1891 : 607-625) in which picric acid rose 

 21.9^ in an oak. 



Experiments in which boiled parts of plants conducted water 



"Osmometers, so-called, are not commonly used as real "measures " of osmosis ; 

 osmoscope would be a much better word. 



