II 



ASCENT OF SAP IN STEMS 



3S 



The flagging of the leaves appears to be the more rapid 

 the more completely the closing of the lumina has been 

 effected. 



When the lumen is closed an upward passage of liquid is 

 still maintained in the wall, but this is probably much too 

 feeble to meet the wants of the leaves. 



Paraffin casts of tracheae. Owing to its extreme 

 mobility the penetration of the paraffin is very complete in 

 these experiments. Thus it was found easy by its means 

 to demonstrate the continuity of the tracheal elements 

 forming the vessels in lime, sycamore, and elm. For this 



id 





/y - : //' ..V 



%m > U\Vt 



V\W > 



&j! 





Paraffin Casts of Vessels. 



Fig. 5. Tin a 



MICROPHYLLA. 



Fig. 6. Tima 

 microphylla. 



7. 



Fig 



Ulmus campestris. 



lengths of 35 cm. were used and the wood of the branches 

 injected as described above was removed with sulphuric 

 acid. It is necessary to anchor the branch by a leaden 

 weight in a deep vessel of the acid. A single night suffices 

 in many cases to remove the wood and leave the paraffin 



r> 2 



