Ill 



ASCENT OF SAP IN STEMS 



61 



ultimate blackening. The contraction which occurs is not 

 of the nature of plasmolysis ; for more than a day is often 

 required for its production, and it cannot be undone by 

 the transference of the leaf to water. 



In each case a sample of sap centrifuged from the fresh 

 branch was tested ; other similar tests were made upon 

 that centrifuged from a branch immediately after steaming, 

 or centrifuged from a branch steamed a day or two pre- 

 viously, or with the liquid centrifuged from a branch which 

 had a day or two previously been steamed, and at once 

 depleted of its sap by centrifuging, and refilled with dis- 

 tilled water. These two last tests were made in order to 

 see if the poisonous materials are set free immediately 

 into the sap on steaming, or whether they are produced as 

 subsequent degradation-products of the cells. 



Table 5. 



Day of Experiment. 



1st. 



Ilex aquifvlium, fresh 



,, ,, steamed direct .... 



,, ,, ,, indirect : ... 



,, + water 1 

 Primus cerasus, fresh 



,, ,, steamed direct 



,, ,, ,, indirect + water 

 Cot oneast er frigida, fresh 



,, ,, steamed indirect . . . 



,, ,, ,, 4- water 

 Salix babylonica, fresh ! . . . 



,, ,, steamed indirect . . . . 



,, ,, ,, ,, + water 

 Sijringa vulgaris, fresh 



,, ,, steamed direct 



,, ,, ,, indirect . . . . 



+ water 





 

 

 









 





 



? 





 

 





 



1 



1 



2nd. 3rd. 



4th. 









 

 

 



+ 









 1 



+ 





 

 







+ 

 + 

 + 









 

 

 



+ 

 + 

 



+ 

 + 







2 





 



+ 

 + 

 + 





 

 

 

 



+ 

 + 







+ 

 + 







+ 

 + 







+ 

 + 

 + 



5th. 





 

 

 







+ 

 + 







+ 

 + 







+ 

 + 







+ 

 + 

 + 



In Table 5, the sap obtained by centrifuging immedi- 

 ately after steaming is termed ' steamed direct " ; 



1 When the sap had stood in contact with the dead cells for two or more 

 days, discoloration of the veins and blackening of some of the cells without 

 marked contraction occurred on the fifth day. 



