420 



UYPEliTROPllY. 



the " uovoli of the olive" and the "burrs" that are 

 formed on some varieties of apple, from w^hich both 

 roots and leaf-shoots are produced in abundance. 



A distinction must be drawn between those instances 

 in which the swelling is solid throughout from the 

 excessive formation of cellular tissue, and those wherein 

 it is hollow from the more rapid growth of the outer 

 as contrasted with the inner portions. These latter 

 cases might be classed under the head of distension. 



Enlargement of the buds may be seen in the case of 

 bulbs and tubers. Occasionally these organs are 

 developed in the axils of leaves, when their nature 



Fio. 201. Formation of tubers or hypertrophied buda in the axils of 

 leaves in the potato. 



