14 



Henry H. Dixon. 



base and was supplied with an eosin solution, which in 24 hours rose 

 to the highest leaves. 



In this experiment the respiration of the medullary ray cells 

 must have been greatly reduced, yet the transpiration stream was 

 not noticeably interfered with. Hence the assumed function of the 

 radial passages and that of the medullary ray cells becomes most 

 improbable. 



Strasburger \) records the following experiments in which 

 stems over 10 m in height, cut across at the base and supplied with 

 poisonous fluids drew these fluids to considerable heights. 



Name 



Fluid 



Time 



Heiffht attained 



Wistm'ia sinensis 



Robinia Pseudacacia 



n n 



Hedera Helix 



Populus dilatata 

 Acer platanoides 



Fagus silvatica 

 Picea vulgaris 

 Pinus Laricio 



Eosin- Alcohol 

 Eosin- Alcobol Copper sulphate 

 10^0 Copper sulphate 

 10% „ 



36 "/o „ 

 3 7o Phenol with Eosin 

 Eosin-Alcohol 



5 % Copper sulphate 



15% 



5% 



5% 

 10% 



5% 



5% 



Strasburger does not fail to point out that the living ele- 

 ments of the wood traversed can have had nothing to do with the 

 elevation of the fluid in the later stages of these experiments, but 

 that some physical process must account for its rise. Consequently 

 we must give up the hypotheses which regard the vital properties 

 of the wood-cells as indispensible to the rise of water in plants. 



Schwenden er 2) criticised this standpoint and suggested that 

 in Stras burger's experiment the living cells, exerted their forces 

 on the upper diluted surface of the poisonous stream, and stated that 



^) E. Strasburger, loc. cit., pp.611 et seq. 



") S. Schwendener, Zur Kritik der neuesten Untersuchungen über das Saft- 

 steigen. Sitzb. d. Akad. d. Wiss. z. Berlin. 1892. 



