REGIONS OP A WOODY STEM. 153 



paraffined or tallow-coated paper. It will keep for years. 

 The proportions of ingredients may be varied. Adding 

 tallow softens wax, adding rosin hardens it. Before applying 

 it rub the hands with tallow. A good way to soften it 

 for working is by putting it in warm water. 



Regions of a Woody Stem. — In connection with grafting 

 teach the nature and use of the regions in a woody branch — 

 pith, wood and bark. Pith consists of empty cells that were 

 once full of living protoplasm like the cells among the bark 

 fibres. The wood shows annual additions produced in the 

 cambium layer. It is in the young wood that the raw fluids 

 from the root ascend to the leaves, see experiment with 

 willow twigs, page 157. Outside of the cambium layer are the 

 bundles of fibres and vessels, making a path for the circulation 

 of the digested liquids, and the thin-walled cells filled with 

 living protoplasm protected externally by the cuticle or scaly 

 bark. The union in grafting begins in the thin layer from 

 the cambium to the cuticle. 



For further study of the rings and grain of wood see 

 "Public School Nature Study," pp. 113-116, with plate. 



Exogenous Stem.— An apple stem, showing pith, nineteen annual rings of wood, 

 cambium film, soft bark and hard bark. If this were grafted the soft uninjured 

 bark of the wedge of the scion would have to be set against the cambium and the soft 

 bark of the stock. 



