Further Growth and Duration of Plants 3 5 



cut off ; the leaves wither and hang on the branches, for no 

 cutting-off layer can be formed. 



When pressing heaths and other small-leaved plants, if they 



Fig. 39. — A. Longitudinal section through the stem and base of the petiole 

 of a poplar. B. Part of the stem and petiole of A more highly magnified. S, 

 stem; P, petiole; V.B. vascular bundle; C, cork tissue; C.S. "separation 

 layer ". (From Farmer's " Practical Introduction to the Study of Botany ".) 



are killed by dipping in boiling water, the leaves are less liable 

 to fall off when the specimens become dry. Plants in press 

 are liable to lose their leaves because darkness and a loss of 

 water are conditions that hasten their fall. 



