the Transpiration- Current. 41 1 
the more completely the closing of the lumina has been 
effected. 
When the lumen is closed there is still an upward passage 
of liquid maintained in the wall, but which is probably much 
too feeble to meet the wants of the leaves. 
\ 
Owing probably to its extreme mobility the penetration of 
the paraffin is very complete in these experiments, We found 
it easy by its means to demonstrate the continuity of the 
tracheal elements forming the vessels in Lime, Sycamore and 
Elm. We experimented up to lengths of 35 cm. by remov- 
ing with sulphuric acid the wood of branches injected as above. 
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 casts of the 
