1902] RISE OF THE TRANSPIRATION STREAM 179 



created a constant demand; the arrangement being "a sort of 

 rude force-pump worked by the wind/' 



Scheit suggested that slight differences in temperature might 

 raise the water **auf deni Wege der Destination *' (1885:477). 

 But, as Scheit himself pointed out, this would not raise any 

 mineral food. 



VI. While the imbibition theory has had no champion since 

 the death of Sachs, it reigned too long to be passed over in a 

 sentence now. Granting Sachs* claim that the imbibition theory 

 was his personal intellectual product and property, it would seem 

 but fair to confine ourselves in discussing it to the final stage of 

 Its evolution. But it w^as in one of its earlier forms, afterward 

 outgrown by its great exponent, that the theory was dominant. 

 Sachs lists the publications in which this theory was developed 

 in his hands in his Vorlesimgen iiber Pfla?izenphysiologie (2d 

 edition, 225 ) . Its period of greatest vogue was about the 

 close of th^ seventies, after the publication of the paper **Ueber 

 die Porositat des Holzes/' The imbibition theory said that the 



r 



water was carried altogether in the walls of the wood elements, 

 where it was absorbed and held by imbibition. The substance 

 of the wood walls was believed to be very remarkable, in "Dass 

 sie (the walls) verhaltnissmassig nur wenig Wasser in sich , 

 aufnehmen, dass dieses wenige Imbibitionswasser jedoch in ihnen 

 auffallend beweglich ist." The removal of any water from the 

 wood at the top of the tree caused a flow toward the point of 

 loss, the demand for water being thus propagated in the walls 

 to the roots, where it could be satisfied. It had been demon- 

 strated that the forces at play in imbibition far more than 

 sufficed for the elevation of the water; that the water moved 

 easily in wood was certain. That it moved in the walls seemed 

 to have been demonstrated by direct observation of air filling 

 the lumina ; by the experiment of Unger (1868), who injected 

 the lumina with wax without preventing the movement of 

 water; and later by Sachs' experiments with sharply bent 

 tendrils, etc. 



Sachs elaborated no new theory of imbibition to account for 



