THE CELL 5 



illustration. In many cases two or more near-lying pits of the same 

 cellular element become confluent as they pass inward, and open 

 into the cavity of the cell by a common aperture. The cement 





FIG. 4. Wood of the spruce (Picea canadensis) , showing ray cells with simple 

 pits and longitudinal water-conducting elements with bordered pits. 



substance is strongly developed here and the thickened walls of 

 the cells are lignified. The pits, in spite of the complications noted 

 above, are to be regarded as simple pits. 



