STEPHEN IIAI.HSS K MM-; HI. Mi-; XT TO DKTIik.MlNK 'I' III-; 

 PRESSl'KIi OF TIIK KLO\V 1- SAP 



(A branch, b, has been cut <>fT and an open glass tube fitted 



over the end, the pressure being indieated by the 



rise of sap in the tube ) 



